Instituto de Sistemas Optoelectrónicos y Microtecnología
Universidad Politécnica de Madrid


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Departamento de Ingeniería Electrónica

Departamento de Electrónica Física

Departamento de Ingeniería Química Industrial y Medio Ambiente

Escuela Técnica Superior de Ingenieros de Telecomunicación

Escuela Técnica Superior de Ingenieros Industriales

Universidad Politécnica de Madrid

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Título: "Improvement of performance and reliability of GaN-based high electron mobility transistors (HEMTs) using high-k dielectrics"
Ponente: Candidata a Doctora Doña Gao Zhan / Directores de Tesis Doctoral: Dr. Fernando Calle Gómez y Dra. María Fátima Romero Rojo
Organismo: Departamento de Ingeniería Electrónica - Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid
Resumen:
Lectura y Defensa de Tesis Doctoral

Fecha: lunes, 11 de septiembre de 2017
Hora: 11:00 horas
Lugar: Salón de Grados, Edificio A de la ETSI de Telecomunicación [Cómo llegar]
 
Título: Tuning the properties of InAs/GaAs quantum dots through a modified capping layer: Application to optoelectronic devices
Ponente: Candidato a Doctor D. Antonio David Utrilla Lomas / Director de Tesis Doctoral: Dr. José María Ulloa Herrero
Organismo: Departamento de Ingeniería Electrónica - Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid
Resumen:
Lectura y Defensa de Tesis Doctoral

Fecha: lunes, 10 de julio de 2017
Hora: 10:30 hora
Lugar: Salón de Grados, Edificio A,- 128.1, E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid [Cómo llegar]
 
Título: Epitaxial Growth and Characterization of InGaN layers for photovoltaic applications
Ponente: Candidato a Doctor D. Víctor Jesús Gómez Hernández/ Directores de Tesis Doctoral: Dr. Miguel Ángel Sánchez García y Dr. Javier Grandal Quintana
Organismo: Departamento de Ingeniería Electrónica - Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid
Resumen:
Lectura y Defensa de Tesis Doctoral

Fecha: viernes, 30 de junio de 2017
Hora: 11:30 hora
Lugar: Salón de Grados, Edificio A,- 128.1, E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid [Cómo llegar]
 
Título: Development and characterization of graphene-based electronic devices
Ponente: Candidato a Doctor D. Alberto Boscá Mojena/ Directores de Tesis Doctoral: Dr. Fernando Calle Gómez y Dr. Javier Martínez Rodrigo
Organismo: Departamento de Ingeniería Electrónica - Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid
Resumen:
Lectura y Defensa de Tesis Doctoral

Fecha: viernes, 23 de junio de 2017
Hora: 11:00 hora
Lugar: Salón de Grados, Edificio A,- 128.1, E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid [Cómo llegar]
 
Título: Progress and challenges in electrically pumped GaN-based VCSELs
Ponente: Åsa Haglund
Organismo: Photonics Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology, Göteborg, Sweden
Resumen:
The Vertical-Cavity Surface-Emitting Laser (VCSEL) is the preferred light source in many applications areas such as short-distance optical communication links, optical navigation and tracking, gas sensing, and optical encoding. Its low power consumption, easy integration into two-dimensional arrays, and low-cost manufacturing also make this type of semiconductor laser suitable for application areas such as high-resolution printing, general lighting, and biomedical applications. However, these applications require emission wavelengths in the blue-UV instead of the established infrared regime, which can be achieved by using GaN-based instead of GaAs-based materials. The development of GaN-based VCSELs is challenging, but during recent a few groups have managed to demonstrate electrically pumped GaN-based VCSELs with an optical output power around 1 mW with decent threshold current densities. The performance is limited by challenges such as achieving high-reflectivity mirrors, optical mode and carrier confinement, efficient transverse current spreading, and accurate cavity length control. This talk will summarize different strategies to solve these issues in electrically pumped GaN-VCSELs together with state-of-the-art results. We will highlight our work at Chalmers University of Technology on combined transverse current and optical mode confinement, where we show that many structures used for current confinement result in unintentionally optically anti-guided resonators. Such resonators can have a very high optical loss, which easily doubles the threshold gain for lasing. We will also present our results on electrically conductive distributed Bragg reflectors (DBRs) in AlN/GaN and GaN/ZnO, as well as an alternative to DBRs; TiO2/air high contrast gratings (HCGs).

Fecha: viernes, 2 de junio de 2017
Hora: 11:30 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Deep levels and acceptors in Zn(Mg)O: effect of N-doping
Ponente: Candidato a Doctor D. Alejandro Kurtz de Griñó/ Director de Tesis Doctoral: Dr. Adrián Hierro Cano
Organismo: Departamento de Ingeniería Electrónica - Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid
Resumen:
Lectura y Defensa de Tesis Doctoral

Fecha: viernes, 19 de mayo de 2017
Hora: 10:00 hora
Lugar: Salón de Grados, Edificio A,- 128.1, E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid [Cómo llegar]
 
Título: Fabrication of superior 2D and 3D nano-devices using NanoFrazor lithography
Ponente: Felix Holzner
Organismo: SwissLitho AG, Technoparkstrasse 1, Zurich, 8005, Switzerland
Resumen:
Thermal scanning probe lithography (t-SPL) has recently entered the lithography market as first true alternative or extension to electron beam lithography (EBL). The first dedicated t-SPL systems, called NanoFrazor, have been installed at research facilities in Europe, America, Asia and Australia by the company SwissLitho, a spinoff company of ETH Zurich. Core of the technology - which has its origins at IBM Research and their Millipede project - is a heatable ultra-sharp probe tip which is used for patterning and simultaneous inspection of complex nanostructures. The heated tip creates arbitrary depth, high-resolution (<10 nm half-pitch) nanostructures by local evaporation of resist materials. Using an integrated in-situ metrology method, the patterning depth can be controlled with 1 nm accuracy. This enables patterning of extremely accurate 3D nanostructures in a single step without wet development. The patterning speed is comparable to high resolution EBL. The application range for this new nanofabrication capability is broad and will be demonstrated with the discussion of a selection of examples. Applications that are enabled by the nm-precise 3D patterning include 3D phase plates and finely tuned coupled Gaussian optical microcavities. Furthermore, 3D shaped nanofluidic confinements have been used to precisely control the movement of nanoparticles and nanowires. The high resolution 2D capability was applied e.g. to shape complex plasmonic structures. Furthermore, several superior nanoelectronic devices will be shown. Such devices are predominantly made from randomly dispersed nanowires or 2D materials. Therefore, they benefit strongly from the unique markerless overlay capability of the NanoFrazor lithography, but also from the fact that actually no charged particle beam is used during lithography, which can often damage sensitive materials. Finally, a few examples are shown, how the heated tips are also used for direct modification of surfaces by triggering of a local phase change or a chemical reaction.

Fecha: miércoles, 17 de mayo de 2017
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Simulation Insights into Electronic Properties of Organic Semiconductors
Ponente: Nenad Vukmirovic
Organismo: Scientific Computing Laboratory, Institute of Physics Belgrade
Resumen:
Organic semiconducting materials exhibit complex atomic structures with a lack of periodicity that lead to charge carrier localization which, in turn, strongly affects electronic transport properties of these materials. To understand charge carrier localization and electronic transport in organic semiconductors, simulations that take into account the details of the atomic structure of the material are of utmost importance. Computational methods that can be used to simulate the electronic properties of organic semiconductors will be reviewed and an overview of some results that have been obtained from such simulations will be given. It will be shown that in ordered conjugated polymer materials thermal disorder of main chains leads to wave function localization. In small molecule based organic semiconductors, grain boundaries introduce localized trap states at the points where electronic coupling between the molecules from different sides of the boundary is the strongest. On the other hand, at the boundary between domains in polymer based materials such localization does not occur.

Fecha: martes, 9 de mayo de 2017
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Seminar on security and safety rules to be applied in case of emergency within the ISOM laboratories
Ponente: Dr. Javier Martínez Rodrigo
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid
Resumen:

Fecha: lunes, 20 de febrero de 2017
Hora: 11:30 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Growth of Nitride-based Nanocolumn for Optical Device and Monolithic Integration of Si-MOSFET and GaN micro-LED
Ponente: Prof. Hiroto Sekiguchi (Toyohashi University of Technology)
Organismo: Toyohashi University of Technology
Resumen:
Education: 2010 Ph. D. (Engineering) Department of Electrical and Electronics, Sophia University Faculty academic appointments: 2010-2013 Assistant Professor, Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology 2013-2015 Lecturer, Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology 2015- Associate Professor, Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology Themes of Research (in Toyohashi University of Technology): /Growth and optical property of Rare-earth doped GaN grown by MBE /Growth of InGaN-based nanocolumns /Device process for monolithic integration of Si-LSI and GaN optical devices

Fecha: lunes, 6 de febrero de 2017
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Sistemas de almacenamiento de energía basados en grafeno
Ponente: Dr. Jorge Pedrós Ayala
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid
Resumen: [Archivo]

Fecha: lunes, 6 de febrero de 2017
Hora: 9:30 hora
Lugar: Sala de Seminarios del Departamento de Ciencia de Materiales. ETS Ingenieros de Caminos, Canales y Puertos. UPM [Cómo llegar]
 
Título: InxGa1-xN layers, nanowires, and nanodots on Silicon for clean energy applications
Ponente: Candidato a Doctor: D. Pavel Aseev/Directores de Tesis Doctoral: Dr. Enrique Calleja Pardo y Dr. Zarko Gacevic
Organismo: Departamento de Ingeniería Electrónica - Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid
Resumen:
Lectura y Defensa de Tesis Doctoral

Fecha: martes, 17 de enero de 2017
Hora: 11:00 hora
Lugar: Salón de Grados, Edificio A,- 128.1, E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid [Cómo llegar]
 
Título: Desarrollo de Superficies Nanoestructuradas para Biosensores Ópticos y Sensores Biomiméticos
Ponente: Candidato a Doctor D. Víctor Canalejas Tejero/ Director de Tesis Doctoral: Dr. Carlos Angulo Barrios
Organismo: Departamento Ingeniería Electrónica - Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM) de la E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid
Resumen:
Lectura y Defensa de Tesis Doctoral

Fecha: lunes, 14 de noviembre de 2016
Hora: 12:00 hora
Lugar: Salón de Grados, Edificio A,- 128.1, E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid [Cómo llegar]
 
Título: GaN. The journey from two special atoms to center stage at the communication revolution
Ponente: Dr. José Jiménez, Fellow of Device Physics de Qorvo (Oregon, USA)
Organismo: Device Physics de Qorvo. Qorvo, Inc., Richardson, TX (Oregon, USA)
Resumen:
In this seminar, we will explore how and why GaN has become an essential part of the next wave of communication infrastructure systems and describe the current research topics within this area. The emphasis will be not in the detail of technical theoretical or experimental breakthroughs, but in separating what is unique on this technology both in capabilities and challenges.

Fecha: lunes, 17 de octubre de 2016
Hora: 12:00 hora
Lugar: Salón de Grados, Edificio A,- 128.1, E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid [Cómo llegar]
 
Título: Crecimiento y caracterización de películas delgadas de Bi electrodepositadas sobre sustratos de n-GaAs
Ponente: Candidata a Doctora: Dª Alicia Prados Díaz/Directores de Tesis Doctoral: Dra. Rocío Ranchal y Lucas Pérez
Organismo: Facultad de CC. Físicas de la UCM-Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM)
Resumen:
Lectura y Defensa de Tesis Doctoral

Fecha: miércoles, 21 de septiembre de 2016
Hora: 12:00 hora
Lugar: Sala de Grados de la Facultad de CC. Físicas de la UCM [Cómo llegar]
 
Título: Control of surface kinetics during the growth of III-nitrides on native substrates
Ponente: Zlatko Sitar, Kobe Steel Distinguished Professor
Organismo: Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695-7919, USA
Resumen:
AlGaN alloys are the building blocks of deep UV optoelectronics and high-power devices. Metal polar, Al-rich AlGaN films were grown on both single crystalline AlN and sapphire substrates. The role of dislocation density on surface kinetics and morphology of these thin films will be presented. With the reduced dislocation density of the films grown on AlN substrates, atomically smooth bilayer stepped surfaces are achieved with RMS roughness of less than 50 pm. By controlling the surface supersaturation during MOCVD growth, a transition from 2D nucleation to step flow was achieved. Depending on growth conditions, a critical substrate misorientation angle for onset of step-bunching was observed. In order to predict and control the surface morphology, an all-inclusive surface kinetic framework was developed that connects vapor supersaturation, surface supersaturation, surface diffusion length, and substrate misorientation angle. In general, transitioning from a surface with 2D nuclei to one with bilayer steps required a decrease in supersaturation or an increase in miscut, whereas the suppression of step-bunching required the two parameters to change in the opposite direction. The composition of bilayer stepped AlGaN was found to strongly depend on substrate misorientation angle. Step-bunching resulted in compositional inhomogeneity as observed by photoluminescence and scanning transmission electron microscopy studies. The talk will discuss MOCVD processes for control of AlGaN composition and heteroepitaxy, approaches to control strain, point defects, and doping in this material, and implications of this technology for further development of UV optoelectronic and electronic devices.

Fecha: viernes, 9 de septiembre de 2016
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Si-based Tandem and Multijunction Solar Cells Using III-V Compounds
Ponente: Prof. Steven A. Ringel. Neal A. Smith Chair Professor of Electrical and Computer Engineering. Executive Director, Institute for Materials Research (IMR. Faculty Director, Materials & Manufacturing for Sustainability (M&MS). The Ohio State University
Organismo: The Ohio State University

Resumen:

Fecha: jueves, 14 de julio de 2016
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Investigations on III-Nitrides nanostructures: application to Renewable Energies and Bio-Sensing
Ponente: Candidato a Doctor: D. Paul Eduardo David Soto Rodríguez/Directores de Tesis Doctoral: Dr. Enrique Calleja Pardo y Dr. Zarko Gacevic
Organismo: Departamento Ingeniería Electrónica - Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM) de la E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid
Resumen:
Lectura y Defensa de Tesis Doctoral

Fecha: miércoles, 29 de junio de 2016
Hora: 10:30 hora
Lugar: Sala de Juntas del edificio A, E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid [Cómo llegar]
 
Título: "3D Graphene for Energy Storage". Simposio Internacional: Materiales bidimensionales: explorando los límites de la física y la ingeniería
Ponente: Prof. Fernando Calle (ISOM-DIE-ETSIT UPM)
Organismo: Fundación Ramón Areces

Resumen:
Graphene stands out by many different properties (electrical, optical, structural, mechanical, thermal, etc.), which combinations allow to improve device performance or enable new applications. Perhaps, energy storage by means of supercapacitors and batteries is the main short-term field in which graphene will be exploited. Graphene can be prepared by several techniques. Chemical vapor deposition (CVD) using catalytic metal foils or films has demonstrated very good results for quality single or fewlayer 2D graphene. Similarly, 3D graphene structures are grown by CVD on Cu or Ni metal foams or sponges, showing a high surface useful for supercapacitor electrodes. The graphene foam (GF) processing involves material growth, substrate removal and, eventually, functionalization. We are using plasma enhanced CVD to grow the graphene coating on a metal foam acting as a catalytic mesh. The coating thickness depends on the metal substrate and the growth conditions (gases ratio, growth time, etc.). A free-standing GF is obtained by wet etching the metal substrate. Finally, the GF may be functionalized by different techniques and materials (polymerisation, electrodeposition, sol-gel), either to modify the graphene properties and/or to provide robustness to the 3D structure. In this work we will discuss several demonstrations of GF-based electrodes for supercapacitors, either by filling the GF with a hierarchical polymer nanostructure, or different oxides by electrodeposition or sol-gel. GFs can also be exploited to enhance the properties of batteries or other energy applications. Acknowledgement. This work has been supported by Repsol (Inspire) and Ministerio de Economía y Competitividad (Project ENE2013-47904-C3-1)

Fecha: miércoles, 22 de junio de 2016
Hora: 13:00 hora
Lugar: Salón de Actos, Fundación Ramón Areces, c/ Vitruvio, 5. 28006 Madrid (Spain) [Cómo llegar]
 
Título: Exploring single semiconductor nanowires using a synchrotron nanoprobe
Ponente: Gema Martínez Criado
Organismo: Instituto de Ciencia de Materiales de Madrid (CSIC)
Resumen:
Semiconductor nanowires offer new opportunities for optoelectronic and spintronic nanodevices. However, their full potential is ultimately dictated by our ability to control multiple property-function relationships taking place at the nanoscale in the spatial and time domains. Only a combination of highresolution analytical techniques can provide a comprehensive understanding of their complex functionalities. Here we describe how a multimodal hard X-ray nanoprobe addresses fundamental questions in nanowire research. Selected topics ranging from cluster formation, dopant segregation, and phase separations to quantum confi nement effects are investigated with sub- 100 nm spatial resolution and sub-50 ps temporal resolution. This approach opens new avenues for structural, composition and optical studies with broad applicability in materials science.

Fecha: viernes, 27 de mayo de 2016
Hora: 13:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Nanocintas de FeCo para Aplicaciones en Sensores Magnéticos y Biotecnología
Ponente: Candidato a Doctor: D.Manuel Abuín Herráez/ Directores de Tesis Doctoral: Dr. Marco Maicas Ramos y Dra. Arantzazu Mascaraque Susunaga
Organismo: Facultad de Ciencias Físicas, UCM - ISOM-ETSIT, UPM
Resumen:

Fecha: jueves, 26 de mayo de 2016
Hora: 12:00 hora
Lugar: Sala de grados, Facultad de Ciencias Físicas, UCM. [Cómo llegar]
 
Título: Atomic Layer Deposition: A powerful materials deposition technology
Ponente: Dra. Mercedes Vila Juárez
Organismo: CTECHNANO

Resumen:
Different from chemical vapor deposition (CVD) and physical vapor deposition (PVD), atomic layer deposition (ALD) is based on saturated surface reactions. In this case, the thin films are grown in a layer-by-layer fashion allowing sub-nanometer thickness control, low temperature depositions, good uniformity and superior step coverage on high specific surface area components compared to CVD and PVD. These advantages of ALD over other thin film deposition processes have been conventionally applied mainly in semiconductor electronic industry on the preparation of layers of outstanding High-K dielectric materials. But, due to the advances in tool design and recipe development, the importance of ALD is rapidly expanding for producing innovative nanoscale materials. ALD potential applications are highly multidisciplinar. It has an emerging potential on photovoltaic cells, flexible electronics, enhanced performance glass, paper and textiles, decorative coatings, new generation transistors, sensors, and advanced energy materials technology. Innovations brought by nanotechnology to biosciences, especially in lab-on-a chip tools and biosensors are also proving to be good candidates to benefit from these potentialities.

Fecha: miércoles, 16 de marzo de 2016
Hora: 11:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Seminario sobre Seguridad en el ISOM
Ponente: Prof. Claudio Aroca, Subdirector del ISOM
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid
Resumen:

Fecha: martes, 12 de enero de 2016
Hora: 10:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Design, Technology and Characterization of Micromechanised Sensors and Actuators for Harsh Environments
Ponente: Candidato a Doctor D. Eugenio Sillero Herrero/ Director de Tesis Doctoral Dr. Fernando Calle Gómez
Organismo: Departamento Ingeniería Electrónica - Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM) de la E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid
Resumen:
Lectura y Defensa de Tesis Doctoral

Fecha: martes, 12 de enero de 2016
Hora: 11:00 hora
Lugar: Sala de Grados 128.1, del Edificio A, en la E.T.S.I. Telecomunicación, Universidad Politécnica [Cómo llegar]
 
Título: Large-scale synthesis of ultrathin layered MoO3 by van der Waals epitaxy
Ponente: Aday Molina, Ph.D. Student
Organismo: Low Temperatures Laboratory. Dept. Condensed Matter Physics, 01.03.201 Faculty of Science. Universidad Autónoma de Madrid
Resumen:
Research on layered semiconductors has attracted attention in the last few years due to their interesting and novel properties and their potential applications. Many layered materials, like Mo- or W-based dichalcogenides (transition metal dichalcogenides, TMDCs), are well characterized in their bulk form, but their properties in a two-dimensional configuration are still being studied. The most attractive features of these two-dimensional semiconductors are found in their electronic and optoelectronic properties, especially for applications like nanoscale field-effect transistors or ultrathin photodetectors. In this talk, I am going to talk about the synthesis of large-scale and highly oriented ultrathin MoO3 layers using a simple atmospheric pressure van der Waals epitaxy growth on muscovite mica substrates, that can be easily transferred to a selected substrate (like SiO2) by a deterministic transfer method. Three-electrode (source-drain and back gate) devices are fabricated using the as-grown MoO3 extended and ultrathin layers for optoelectronic applications, finding responsivities of 30 mA.W-1 in the UV region of the spectrum.

Fecha: viernes, 13 de noviembre de 2015
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. Universidad Politécnica de Madrid. [Cómo llegar]
 
Título: High temperature superconductivity
Ponente: Dra. Belén Valenzuela
Organismo: Instituto de Ciencia de Materiales de Madrid
Resumen:
In this seminar I will introduce the field of high temperature superconductivity. First, I will start defining superconductivity and the explanation behind it: the BCS theory. Then, I will explain the breakthrough that cuprates, the first high temperature superconductors, pose to the condensed matter community emphasizing the field of strongly correlated electron systems. Finally, I will present the second family of high temperature superconductors, the iron superconductors and I will briefly mention our work into this area.

Fecha: viernes, 6 de noviembre de 2015
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. Universidad Politécnica de Madrid. [Cómo llegar]
 
Título: Crystallographic Polarity in Selective-Area Gallium Nitride Nanowire Growth: Which End Is Up?
Ponente: Dr. Matthew Brubeck
Organismo: National Institute of Standards and Technology (NIST) The Gaithersburg, Md., and Boulder, Colorado, US.
Resumen:
Increasingly, crystallographic polarity is recognized as a key parameter in Gallium Nitride nanowire (GaN NW) growth. However, an ambiguity exists for NWs grown on Si (111) substrates, where there is no predetermined orientation in the crystallographic polarity. In this talk, we present growth and characterization strategies for obtaining polarity-controlled nucleation layers on Si (111) and their use in spontaneous-nucleation and selective-area growth processes. In particular, we find that long-range selectivity can be obtained for N-polar selective-area NW growth that independent of NW pitch spacing. These ordered NW arrays are a convenient platform for growth of core-sleeve structures and measurement of the surface recombination velocity (SRV), an important metric in high surface-to-volume nanostructures.

Fecha: lunes, 2 de noviembre de 2015
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. Universidad Politécnica de Madrid [Cómo llegar]
 
Título: Propiedades Ópticas y Estructurales de nanoestructuras de Zn(Cd)(Mg)O
Ponente: Candidato a Doctor D. Manuel López Ponce/Directores de Tesis Doctoral: Dr. Adrián Hierro Cano y Dr. José María Ulloa Herrero.
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid.
Resumen:
Lectura y Defensa de Tesis Doctoral

Fecha: lunes, 19 de octubre de 2015
Hora: 11:00 hora
Lugar: Sala de Grados 128.1, del Edificio A, en la E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid. [Cómo llegar]
 
Título: CMOS integration of AlN based piezoelectric microcantilevers
Ponente: Candidata a Doctora Doña Ana Pérez Campos/Director de Tesis Doctoral, Dr. Gonzalo Fuentes Iriarte
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM) de la E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid
Resumen:
Lectura y Defensa de Tesis Doctoral

Fecha: viernes, 24 de julio de 2015
Hora: 11:00 hora
Lugar: En Sala B-223, edificio García Redondo de la E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid [Cómo llegar]
 
Título: Self assembled and ordered group III nitride nanocolumnar structures for light emitting applications
Ponente: Candidato a Doctor D. Steven Albert/ Director de Tesis Doctoral: Dr. Miguel Ángel Sánchez García
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM) de la E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid
Resumen:
Lectura y Defensa de Tesis Doctoral

Fecha: viernes, 29 de mayo de 2015
Hora: 12:00 hora
Lugar: Sala de Grados 128.1, del Edificio A, en la E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid [Cómo llegar]
 
Título: Seminario de Prácticas de buen uso de Bombas de Vacío
Ponente: Los representantes oficiales de bombas de vacío de Edwards en España y Portugal
Organismo: Edwards Ibérica Vacuum
Resumen:
Prácticas de buen uso de Bombas de Vacío

Fecha: jueves, 28 de mayo de 2015
Hora: 11:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. Universidad Politécnica de Madrid [Cómo llegar]
 
Título: Hydride VPE for current III-V and nitride semiconductor compound issues
Ponente: Prof. Agnes Trassoudaine
Organismo: Université Blaise Pascal - Clermont-Ferrand II, Clermont-Ferrand
Resumen:

Fecha: lunes, 11 de mayo de 2015
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. Universidad Politécnica de Madrid [Cómo llegar]
 
Título: Technology and characterization of GaN-HEMTs devices: high temperature and trapping effects
Ponente: Candidata a Doctora Doña Sara Martín Horcajo/Director de Tesis Doctoral, Dr. Fernando Calle Gómez
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM) de la E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid
Resumen:
Lectura y Defensa de Tesis Doctoral

Fecha: jueves, 26 de marzo de 2015
Hora: 12:00 hora
Lugar: Sala de Grados 128.1, del Edificio A, en la E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid [Cómo llegar]
 
Título: Surface InGaAs nanostructures for sensing applications
Ponente: candidata a Doctora Doña María José Milla/Director de Tesis Doctoral, Dr. Álvaro de Guzmán Fernández González
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid.
Resumen:
Lectura y Defensa de Tesis Doctoral

Fecha: viernes, 27 de febrero de 2015
Hora: 11:00 hora
Lugar: Sala de Grados 128.1, del Edificio A, en la E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid [Cómo llegar]
 
Título: Máster de Ingeniería de Materiales "New Materials and Emerging Technologies"
Ponente: Organizado por Prof. Fernando Calle
Organismo: Universidad Politécnica de Madrid
Resumen:
Entrepeneurship in Materials Round Table among top representatives of several companies of different sectors of Materials, including Chairman: Arístides Senra, OTRI-UPM. Silvia Rodríguez,bq (ICT,3D printers), http://www.bq.com/catedra-bq/. Miguel Holgado, BioD (biotechnology), http://www.biod.es/. Rocío San Román, Micromag (security), http://www.micromag.es/. Ambiorn Wennberg, Nano4Energy (energy), http://www.nano4energy.eu/. More information in the blog of actúaupm, http://actuaupm.blogspot.com.es/2015/02/18-febrero-bq-biod-micromag-y.html.

Fecha: miércoles, 18 de febrero de 2015
Hora: 16:00 hora
Lugar: ETSI Caminos, Sala de Seminarios. Universidad Politécnica de Madrid [Cómo llegar]
 
Título: III-Nitrides for solid state lighting: the road from white light generation to the 2014 Nobel Prize Physics Award
Ponente: Prof. Enrique Calleja Pardo, Director del ISOM.
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación, Universidad Politécnica de Madrid
Resumen:
El Instituto de Ciencia de Materiales de Madrid organiza esta charla dentro del ciclo de COLLOQUIA. www.icmm.csic.es/seminarios Abstract: The discovery in 1962 of solid state light sources based on semiconductor materials (Light Emitting Diodes, LED) provided emission in the infrared spectral range. Later, Monsanto and Hewlett Packard commercialized red and green LEDs with multiple applications. The lack of efficient emitters in the blue hindered the development of white light emitters, either by mixing the fundamental colors (RGB), or by color conversion (phosphors). In that context, the work by Amano, Akasaki and Nakamura led them to win the Nobel Prize Physics Award in 2014. In this presentation the basics of LED performance will be revised, emphasizing the generation of white light. The major problems overcome by the Nobel Prize awardees, as well as the still pending issues that delay a full LED commercialization in broad areas will be addressed. The main properties and fabrication aspects of III-Nitride alloys (InGaN) by epitaxial techniques, such as Molecular Beam Epitaxy (MBE) and Metal Organic Vapor Phase Epitaxy (MOVPE) will be presented as the core of the technological development of blue and white LEDs. Nowadays nano-science and nano-technology play a fundamental role in designing and fabricating new devices, not only LEDs, but also single photon sources, solar cells and nano-sensors for gas, chemicals, and biological molecules. A brief survey of such possibilities will also be discussed

Fecha: lunes, 19 de enero de 2015
Hora: 12:00 hora
Lugar: Salón de Actos del ICMM, campus de la Universidad Autónoma de Madrid (campus de Cantoblanco). C/ Sor Juana Inés de la Cruz, 3.28049 Madrid. [Cómo llegar]
 
Título: Actual technological applications of graphene
Ponente: Dr. Javier Martínez Rodrigo.
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación,Universidad Politécnica
Resumen:
A decade ago, researchers Geim and Novoselov amaze the world with the discovery of a material formed with a single layer of atoms: graphene. This material is very versatile due to their exceptional properties, such as electrical, optical or mechanical and is proposed to be used in a wide range of applications ranging from flexible electronic s to energy storage. In all these applications is offered the promise of significantly improving existing products and the possibility of designing materials and devices with new functionality. But the reality is different, since there is only on the market a small number of products based on graphene. This is because the main problem for the introduction of graphene in industrial applications is the lack of methods for the large scale production of graphene materials. Furthermore, the development of graphene materials and devices is more mature in some areas, such as conductive inks or flexible electronics, but in other is in a more conceptual stage, such as biomedicine and aerospace technologies. In this seminar, the fundamental properties of graphene that are relevant to actual industrial applications are reviewed, and the opportunities and challenges of new applications based on graphene technologies are analyzed. Other Seminar: https://www.youtube.com/watch?v=1pGOAMNWRgs

Fecha: lunes, 12 de enero de 2015
Hora: 9:30 horas
Lugar: Sala de Seminarios del Departamento de Ciencia de Materiales. ETSI Caminos, Canales y Puertos, Sótano 1. C/ Profesor Aranguren, s.n. 28040 Madrid. [Cómo llegar]
 
Título: ZnO-based and graphene material systems for green devices
Ponente: Jiro Temmyo, Professor emeritus
Organismo: Shizuoka University, Hamamatsu, Japan
Resumen:
Recently, novel low energy-consumption devices and energy harvesting are expected in terms of efficient regenerative system. Since 2002, we have developed remote-plasma-enhanced MOCVD for ZnO-based ternary alloy system in the 3.75 -1.6eV range. Our demonstrations on MQW LEDs, Schottky PDs and Schottky PVs show a potential of ZnO-based optical devices. In addition, we also discuss graphene system for transparent conducting films and FET channels, which are grown directly on the oxides by alcohol CVD

Fecha: viernes, 10 de octubre de 2014
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Thermal, stress, and traps effects in AlGaN/GaN HEMTs
Ponente: Candidato a Doctor Ashu Wang/Directores de Tesis Doctoral: Prof. Fernando Calle Gómez y Dr. Marko Jak Tadjer
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM). Universidad Politécnica de Madrid
Resumen:
Lectura y Defensa de Tesis Doctoral

Fecha: viernes, 3 de octubre de 2014
Hora: 12:00 hora
Lugar: Salón de Grados del Edificio Sanz Mancebo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Fotodiodos basados en (Zn,Mg)O para la detección de luz ultravioleta
Ponente: Candidata a Doctora Gema Tabares Jiménez/Director de Tesis Doctoral: Prof. Adrián Hierro Cano
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM). Universidad Politécnica de Madrid
Resumen:
Lectura y Defensa de Tesis Doctoral

Fecha: viernes, 19 de septiembre de 2014
Hora: 11:00 hora
Lugar: Edificio García Redondo, B-223. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Electronic Structure and Properties of Transparent Conducting Oxide Semiconductors
Ponente: Prof. Chris Mc Conville
Organismo: Department of Physics, University of Warwick, Coventry CV4 7AL UK.
Resumen:
Oxide semiconductors have become of great technological interest and importance in recent years with enormous opportunities to improve existing materials and device applications. This is particularly true for a sub-group of materials that display both optical transparency and high electrical conductivity, the so-called transparent conducting oxides (TCO's). The fact that some of these materials, such indium tin oxide (ITO), have been around for many years and have seen significant industrial use as transparent conductors in a relatively low quality form, has perhaps contributed to the belated recognition of the possibilities of using these materials as semiconductors in their own right. Here, the surface and bulk electronic properties of epitaxially grown high-quality oxide semiconductors (In2O3,CdO and ZnO) will be discussed and the effects of modifying these surfaces by controlled adsorption and surface treatment. Optical, electronic and structural properties of these semiconducting oxide films will be presented. The valence band density of states and the surface electronic properties of these oxide semiconductors have been studied using high-resolution angle-resolved photoemission spectroscopy (ARPES), while core-level photoemission spectroscopy (HAXPES) has been achieved with hard x-rays (E >2,500 eV), and the results compared with theoretical DFT band structure calculations. A common property of these oxide semiconductors is found to be the presence of an electron accumulation layer at the surface. While this is similar to materials such as InN and In-rich InGaN, it is in marked contrast to the electron depletion typically observed at the surfaces of conventional III-V and II-VI semiconductor materials. More unusual still is the quantized nature of this surface 2D electron gas. Additionally, in these TCO's hydrogen is found to be a donor and any native defects have a propensity to be donors in what are already n-type material. The origins of these phenomena will be discussed in terms of the band structure and intrinsic properties of the materials.

Fecha: lunes, 7 de julio de 2014
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: III-Nitride Nanowire Light Sources
Ponente: Prof. Pallab Bhattacharya
Organismo: Department of Electrical Engineering and Computer Science. University of Michigan, Ann Arbor, MI, USA
Resumen:
In(Ga)N nanowires can be grown catalyst-free on silicon substrates by molecular beam epitaxy with density in the range of 108-1011cm-2. The nanowires grow vertically in the wurtzite crystalline form and the In composition of the nanowire can be varied to produce emission in the range of 366-700nm. Most importantly, extensive structural characterization indicates that the nanowires are relatively free of extended defects. It has also been reported that the measured surface recombination velocity in GaN nanowires is very small and ∼103cm/s. Temperature dependent luminescence of the nanowires does not exhibit effects related to compositional inhomogeneities. Due to radial relaxation of strain during epitaxy, the polarization fields in nanowire heterostructures is significantly smaller than those in bulk heterostructures. This reduces the blue shift of the emission peak with injection due to the quantum confined Stark effect. Single or an array of such nanowires can therefore provide an excellent platform for the realization of advanced light sources with unique characteristics. In this talk I will describe the characteristics of visible light emitting diodes and electrically pumped lasers and single photon sources made with In(Ga)N/GaN disk-in-nanowire heterostructures.

Fecha: lunes, 16 de junio de 2014
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Nitride laser diodes grown by Plasma Assisted MBE
Ponente: Czeslaw Skierbiszewski
Organismo: Institute of High Pressure Physics, Polish Academy of Sciences, Warszawa, Poland
Resumen:
Development of laser projectors and displays depend to large extend on availability of reliable and efficient laser diodes (LDs) operating in true-blue (450-460 nm) and green (520-540nm) spectral range. The active regions of long wavelength nitride based LDs comprise high indium content quantum wells (QWs), therefore extensive efforts are made to understand the growth mechanism of InGaN. Very recently, green LDs at 500-530 nm have been demonstrated in nitride-based structures grown by metal organic vapour phase epitaxy (MOVPE) either on polar, semipolar and nonpolar substrate orientations. On the other hand, progress in understanding the new growth mechanism for nitrides in plasma assisted molecular beam epitaxy (PAMBE) has led to the demonstration of violet laser diodes (410 nm), true-blue (450 nm) AlGaN-cladding free LDs, which in turn has renewed interest in this technology among the MBE community. For PAMBE, the growth mechanism is entirely different from that in MOVPE, and allows for the growth of device-quality nitride structures at temperatures lower by 200-300°C versus those used in MOVPE. Therefore it is highly interesting whether this technology can be useful for high In content structures required for green emitters. The key difficulty for InGaN growth (which can be inferred from its thermodynamic properties) is high nitrogen overpressure required at optimum growth temperature. Therefore we propose to grow InGaN layers with extremely high N flux, maintaining the noninteracting beams conditions in PAMBE by use of efficient vacuum pumps. We had already shown that by increasing the nitrogen flux in PAMBE up to 0.7µm/h we were able to achieve optically pumped lasing from single quantum well (SQW) laser structures in the range of 470-501 nm- In this work we demonstrate AlGaN-cladding free LDs grown by PAMBE which operate in the region of 430-484 nm at the optical powers up to 0.5 W in continuous wave (cw) mode [4,5]. The quantum wells of these LDs were grown at high N flux of 0.7-2µm/h. We used a simplified separate confinement heterostructure design with GaN claddings. The optical modes were confined by the thick 120 nm In0.08Ga0.92N waveguide. We will discuss (a) the InGaN growth mechanisms in PAMBE-in particular the conditions for suppression of In segregation and to achieve sharp interfaces between quantum wells and barriers, (b) the role of claddings and waveguide design on the performance of LDs grown by PAMBE.

Fecha: lunes, 2 de junio de 2014
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Alternativas para el graduado del GITST. Posibilidades de investigación en un centro de investigación (ISOM-UPM)
Ponente: Prof. Miguel Ángel Sánchez-García
Organismo: El Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM) de la Universidad Politécnica de Madrid
Resumen:
Esta sesión está coordinada con una mesa redonda que se celebrará el mismo día de 15 a 16.15 horas, donde se presentarán las principales actividades de varias empresas del sector TIC (Accenture, Deloitte y Telefónica en este semestre) y el rol que los ingenieros de telecomunicación desempeñan en ellas.

Fecha: jueves, 13 de febrero de 2014
Hora: 16:50 hora
Lugar: Salón de Grados del Edificio Sanz Mancebo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Future of multifunctional nanocrystalline ZnO
Ponente: Prof. Durga Basak
Organismo: Indian Association for the Cultivation of Science, Department of Solid State Physics, Calcuta, India
Resumen:
Research on ZnO has been continuing to be at the forefront of several new developments in fields of electrical, optical, optoelectronic, medicine, sensors and medical diagnostics owing to their versatile functional properties. Highly conductive ZnO can be achieved with proper doping, which has been used for creating transparent electronics. Although, a fully ZnO-based optoelectronic device is still remains elusive due to lack of stable, p-type ZnO-, n-type ZnO can be used creatively complement existing devices to create new technology. ZnO, like GaN, is a high bandgap material making it attractive for ultraviolet light sensors, especially, its one-dimensional (1D) structure has shown very high photoconductive gain. ZnO is being widely used as photocatalysts because of their high photosensitivity, photochemical stability, large band gap, strong oxidizing power and non-toxic nature. During the last few years, we have developed ZnO-based transparent conducting oxides (TCO) and also intensively investigated the properties of ultraviolet photoconductivity, and photocatalysis of nanostructured ZnO. We use RF magnetron sputtering and pulsed laser deposition techniques for the growth of TCOs. A low-cost aqueous solution growth method has been used to create nanostructures in ZnO. In the lecture, I will provide an overview on our results on the anomalous UV photoconductivity properties of 1D nanorod arrays of ZnO. The surface effects-including surface band bending, chemisorption/photodesorption of species on the surfaces, and native surface defects/states are more pronounced in the nanostructures than that in thin film and bulk counterparts due to the structural uniqueness and the ultrahigh surface-to-volume (S/V) ratio of ZnO nanostructures. In order to develop the novel application of ZnO nanostructures utilizing the surface effect, it is very important to understand how the physical properties are affected by shrinking the dimension of ZnO. Therefore, in particular, mechanistic insights behind the UV photoconductivity would be discussed. The successful exploitation of semiconductor photocatalysts requires the development of techniques for controlling their size, morphology, structural and surface characteristics, as well as efforts to enhance their photochemical response to UV/visible/solar illumination. In this context, I will illustrate our recent achievements towards ZnO-based composites for organic dye degradation.

Fecha: jueves, 23 de enero de 2014
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Properties and applications of high electron density structures based on InN and related compounds
Ponente: candidato a Doctor Tommaso Brazzini/Director de Tesis Doctoral: Prof. Fernando Calle Gómez
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación,Universidad Politécnica
Resumen:
Lectura y Defensa de Tesis Doctoral

Fecha: viernes, 20 de diciembre de 2013
Hora: 12:00 hora
Lugar: Salón de Grados del Edificio Sanz Mancebo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Nanomechanics and strain engineering in atomically thin MoS2
Ponente: Andrés Castellanos-Gómez
Organismo: Delft University of Technology, 2628 CJ Delft, The Netherlands
Resumen:
Single-layer MoS2 is an attractive two-dimensional material that combines the mechanical flexibility of graphene with a large direct bandgap. While graphene is very interesting as a transparent electrode, its lack of a bandgap limits its usefulness in semiconducting and optoelectronic devices. Atomically thin MoS2, on the other hand, has a large intrinsic bandgap. This attractive feature has been employed to fabricate many devices not possible in graphene, such as field-effect transistors with high mobility and current on/off ratio, logic gates and efficient photo-transistors. Our recent work on MoS2 has been focused on developing new methods to fabricate single layer MoS2 and to characterize the intrinsic mechanical, optical and electrical properties of this atomically thin material. Here, I will show an overview of our last results on MoS2 paying special attention to our studies on nanomechanical resonators based on MoS2 layers and on the effect of localized strain on the optoelectronic properties of MoS2

Fecha: jueves, 17 de octubre de 2013
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Type II InAs/GaSb superlattice infrared photodetectors
Ponente: Wenquan Ma
Organismo: Institute of Semiconductors, Chinese Academy of Sciences, Qinghua East Road A 35, Beijing 100083, China
Resumen:
Type II InAs/GaSb superlattice (SL) is an alternative and a very promising material system for advanced infrared photodetector applications and has been investigated intensively in recent years. InAs/GaSb SL detector covers the detection range of about 2 to 30 µm and has some advantages especially in the long and very long wavelength ranges compared to HgCdTe counterpart. For infrared photodetctor applications, there may have two main hurdles to overcome. One is the growth of high quality SL materials since the optimized growth window is very narrow and the interface control is complicated for the SL materials; the other may lie in an effective device surface passivation in order to suppress the dark current. In this talk, I will present our progress in developing type II InAs/GaSb SL infrared photodetectors. We have grown very high quality InAs/GaSb SL materials by molecular beam epitaxy and have demonstrated detector devices covering the short, mid, long, and very long wavelength ranges. We have aslo demonstrated a narrow-band two-color long-/very-long wavelength photodetector using type II InAs/GaSb SL structures.

Fecha: lunes, 8 de julio de 2013
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Beyond self-assembly: Advanced fabrication and characterization methods applied to unconventional semiconductor nanostructures
Ponente: Dr. Benito Alén
Organismo: Instituto de Microelectrónica de Madrid, Centro Nacional de Microelectrónica (CSIC)
Resumen:
Semiconductor quantum dots (QDs) and nanowires (NWs) are not only fascinating physical nanoobjects but also the key component in many disruptive information technologies and solar energy harvesting concepts. In the last years, considerable progress has been achieved in their fabrication, their physical understanding, and their integration into nanophotonic and nanoelectronic devices. However, conventional self-assembled growth methods lead to the random nucleation position of the nanostructures and may cause severe problems for the deterministic coupling of single nanostructures and devices or in large scale device fabrication. In this seminar, I will present different strategies which enable the fabrication and/or characterization of semiconductor nanostructures beyond self-assembly or in a deterministic way. This includes several unconventional nanostructures like site-controlled QDs, lateral QD molecules and vertical NWs or advanced methods like AFM nanolithography, single photon interferometry and X-ray excited optical luminescence

Fecha: viernes, 5 de julio de 2013
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Applications of ion beam techniques for the study of semiconductors: from growth to processing issues
Ponente: Dr. Andrés Redondo-Cubero
Organismo: Instituto Superior Técnico (Technical Univeristy of Lisbon, Portugal).
Resumen:
The talk will provide an overview of high (MeV) and medium (keV) energy ion beam techniques, focused on the applications to wide bandgap semiconductor materials (GaN, ZnO, and related compounds). The benefits of these depth-profiling non-destructive methods will be discussed extensively, paying attention to the detection of growth problems in epitaxial layers, i.e., the presence of impurities, compositional gradients, strain, phase separation, etc. Beyond the conventional use for growth-related issues, and thanks to the advanced focused microprobes, these techniques can also be applied for the accurate characterization of processed devices (such as control pads and transistors), opening a new way towards quality control.

Fecha: viernes, 14 de junio de 2013
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: In(Ga)N/GaN nanocolumnar structures for solid state lighting
Ponente: Steven Albert
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación,Universidad Politécnica
Resumen:
Self assembled arrays of InGaN/GaN nanocolumnar Light Emitting Diodes (LEDs) always show polychromatic emission, mainly due to an inhomogeneous distribution of NCs geometry (diameter, height), In content, and strain distribution within the active region (QDisc). In addition, self-assembled NCs may merge and generate extended defects (dislocations and stacking faults). Thus, efficient white LEDs based on self-assembled III-nitride nanostructures have little chances to become commercial. During the last years the selective area growth (SAG) of GaN nanocolumns (NCs) on GaN/sapphire substrates has been studied by a number of groups [1-4], and the fabrication of NCs arrays with well controlled position/diameter has been demonstrated. This work reports on the selective area growth of axial and core-shell InGaN/GaN nanocolumnar structures on GaN/sapphire templates with plasma assisted molecular beam epitaxy (PAMBE). In case of the axial InGaN/GaN structures, a three step growth procedure was followed. With an appropriate selection of optimal growth conditions, InGaN NCs emitting in the red, green, and blue spectral range have been fabricated. Once emission wavelength is controlled, white light emission at room temperature is achieved. The core-shell InGaN/GaN structures were fabricated using a combination of top-down and bottom up fabrication. For all samples GaN pillars with a length of around 2 micron were fabricated out of GaN-sapphire templates. After standard degreasing the samples were loaded into a PAMBE system and the InGaN (over)growth was performed aiming for emission in the blue-violet spectral range. A very important issue related to commercial LED applications is the fabrication of ordered InGaN nanocolumnar structures directly on cheap, high quality substrates, like Si, having a well established processing technology. Due to that, the final part of this work reports on the SAG of InGaN/GaN NCs on Si (111) substrates using GaN buffer layers. It is shown that SAG is achieved on GaN buffered Si(111). Moreover, by tuning the growth conditions, InGaN NCs can be grown on top of the GaN NCs thus, allowing the fabrication of full nanocolumnar InGaN/GaN heterostructure LEDs. In addition, NCs morphology was optimized for green InGaN emitters, at around 2.3 eV. It was found that once the appropriate growth temperature is established, an increase in In/Ga ratio and decrease in group(III)/N ratio leads to InGaN NCs with quite homogenous morphology and improved optical quality, as indicated by the IQE value of 37%, estimated from PL.

Fecha: viernes, 7 de junio de 2013
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Ultra-High frequency thin film SAW devices
Ponente: candidato a Doctor: Juan Gabriel Rodríguez Madrid/ Directores de Tesis: D. Fernando Calle Gómez y D. Gonzalo Fuentes Iriarte
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación,Universidad Politécnica
Resumen:
Lectura y Defensa de Tesis Doctoral

Fecha: martes, 4 de junio de 2013
Hora: 11:30 horas
Lugar: Salón de Grados del Edificio Sanz Mancebo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: InGaN semiconductor for novel solar cell applications
Ponente: Pavel Aseev
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación,Universidad Politécnica
Resumen:
Presentation corresponding to the Lab for Optoelectronic Systems and Microtechnology (Master Electronic Systems Engineering)

Fecha: jueves, 30 de mayo de 2013
Hora: 16:00 horas
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Doping difficulties in wide-bandgap oxides for optoelectronics
Ponente: Alejandro Kurtz de Griñó
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación,Universidad Politécnica
Resumen:
Presentation corresponding to the Lab for Optoelectronic Systems and Microtechnology (Master Electronic Systems Engineering)

Fecha: jueves, 30 de mayo de 2013
Hora: 16:30 horas
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: GaAsSbN capped InAs QDs: A new nanostructure-based approach for telecom wavelengths
Ponente: Antonio David Utrilla Lomas
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación,Universidad Politécnica
Resumen:
Presentation corresponding to the Lab for Optoelectronic Systems and Microtechnology (Master Electronic Systems Engineering)

Fecha: jueves, 30 de mayo de 2013
Hora: 17:00 horas
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: InN/InGaN Quantum Dots: A Surprise for Highly Sensitive and Fast Potentiometric Biosensors.
Ponente: Dr. Naveed ul Hassan Alvi
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación,Universidad Politécnica
Resumen:
The development of highly sensitive and fast biosensors with good reproducibility and specificity is the main focus of the biosensing research community because it offers a great opportunity for the diagnosis of many major life threatening diseases and their treatments at early stages. Therefore, the health industry urgently needs the development of more efficient, reliable, and cheap sensing and detection technologies. Towards this goal we demonstrate epitaxially grown InN quantum dots (QDs) for fast, highly sensitive, and efficient potentiometric biosensors owing to their low-dimensionality and unique electronic properties. The InN QDs are grown by plasma-assisted molecular beam epitaxy (PA-MBE) on a 80 nm thick high-In-composition In0.54Ga0.46N layer on a (0001) GaN/sapphire substrate. They are bio-chemically functionalized for the detection of glucose and cholesterol molecules. The such fabricated InN QDs based biosensor exhibits excellent linear electrochemical response with high sensitivity of 80 and 96 mV/decade for glucose and cholesterol molecules over a wide logarithmic glucose and cholesterol concentration range. The InN QDs based biosensor also reveals fast response time of less than 2 seconds with good stability and reusability and shows negligible response to common interferents such as ascorbic acid and uric acid. The InN QDs based biosensors, hence, has full potential to be an attractive candidate for clinical diagnoses and has the potential to replace and compete with other available diagnostic devices. The InN QDs are compared with InN thin films, also grown on a 80 nm thick In0.54Ga0.46N layer, having the same surface properties but different morphology and electronic properties. The sensitivity of the InN QDs based biosensor is twice that of the InN thin film based biosensor, the EMF is three times larger, and the response time is five times shorter. This reveals that the superior biosensing properties of the InN QDs are related to their zero-dimensional nature and not only to the surface properties.

Fecha: viernes, 24 de mayo de 2013
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Dispositivos de Grafeno: 2D y 3D
Ponente: Javier Martínez Rodrigo
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación, Universidad Politécnica
Resumen:
https://www.youtube.com/watch?v=1pGOAMNWRgs

Fecha: lunes, 13 de mayo de 2013
Hora: 9:30 horas
Lugar: Sala de Seminarios del Departamento de Ciencia de Materiales. ETSI Caminos, Canales y Puertos, Sótano 1. C/ Profesor Aranguren, s.n. 28040 Madrid [Cómo llegar]
 
Título: Near-infrared InN quantum dots on high-In composition InGaN
Ponente: Paul Eduardo David Soto Rodriguez
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación,Universidad Politécnica
Resumen:
I will talk on the growth of InN quantum dots (QDs) on thick InGaN layers with high In composition (>50%) by molecular beam epitaxy. Optimized growth conditions are identified for the InGaN layers at reduced growth temperature and increased active N flux resulting in minimized phase separation and defect generation. The InN QDs grown on top of the optimized InGaN layer exhibit small size, high density, and photoluminescence up to room temperature. The InN/InGaN QDs reveal excellent potential for intermediate band solar cells with the InGaN and InN QD bandgap energies tuned to the best match of absorption to the solar spectrum.

Fecha: viernes, 10 de mayo de 2013
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Direct growth of InGaN on Si(111)
Ponente: Dr. Praveen Kumar and Professor Richard Nötzel.
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM). Universidad Politécnica de Madrid in collaboration with BBVA (Chair Nanotechnology)
Resumen:
I will start my presentation with a brief introduction about III-nitrides, especially the novel application potential of InGaN with high In composition and then discuss the main challenges in context with our research: The growth of high-In-composition InGaN directly on Si(111) without any buffer layers-towards novel device designs and the direct integration of III-nitride with Si technology. The growth of InGaN on Si(111) is commonly performed by employing high band gap buffer layers such as AlN or GaN which create an energy barrier to electrically isolate the InGaN layer from the Si substrate. This makes novel device designs complex and costly, if not impossible. Thus, the direct growth of InGaN on Si(111) without any buffer layers is highly desirable. Towards this goal, a series of experiments were performed at various substrate temperatures and Ga, In, and N fluxes on a MECA 2000 MBE system. In a narrow window of growth conditions, laterally extended, micrometer-sized planar areas are formed together with trenches and holes. Detailed structural and optical analyses reveal that the planar areas comprise the InGaN layer with high and uniform In composition, while the trenches and holes are associated with pure GaN and low-In-composition InGaN. Photoluminescence at low temperature is observed from the high-In-composition InGaN layer, which forms an ohmic contact with a p-Si substrate and is large enough to serve as template for planar heterostructure based devices. Associated group members for this work: Paul E. D. Soto Rodriguez, Victor J. Gomez, Naveed H. Alvi and Pavel Aseev

Fecha: viernes, 26 de abril de 2013
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Nonpolar (Zn,Mg)O/ZnO quantum wells: from growth to electroluminescence of a LED structure
Ponente: Prof. J.-M. Chauveau [CVitae]
Organismo: CRHEA, Av. Bernard Gregory, F- 06560 Valbonne Sophia Antipolis, France. University of Nice Sophia Antipolis, Parc Valrose, F-06102 Nice Cedex 2, France.
Resumen:
ZnO-based quantum wells have attracted much attention due to their opportunity of combining band gap engineering, with large excitonic binding energies. So far studies on ZnO have mainly focused on films grown in (0001) orientation. The ZnO-based heterostructures exhibit built-in electric fields along the c-axis, affecting the electronic properties. Non-polar surfaces are of interest since the c-axis of the layer lies in the growth plane in this case. It is expected that QWs structures can be grown without any screening of the exciton binding energies. This property is demonstrated in ZnO/(Zn,Mg)O heterostructures grown on sapphire. Unfortunately the nonpolar QWs grown on sapphire usually exhibit a large density of stacking faults, reducing the emission efficiency. ZnO bulk substrates are commercially available in nonpolar orientations but the as-received substrates require a dedicated annealing procedure to achieve atomically flat surfaces. In this presentation we show a drastic improvement of the structural properties when the QWs are grown on sapphire and on ZnO substrates. On ZnO substrates, we demonstrate the absence of extended defects, a reduced surface roughness and reduced X-Ray FWHM. A strong enhancement of the photoluminescence (PL) with no quantum confined Stark effect properties is also demonstrated compared to the heteroepitaxial QWs (3 orders of magnitude). In addition the polarization dependent PL evidences the expected selection rules in these orientations. Then we shall compare the different nonpolar orientations (m- or a-planes). The PL intensity of an m-plane QW is nearly constant as a function of the temperature up to RT, giving rise to a very high internal quantum efficiency. The origin of this observation was studied by time resolved PL, which demonstrates the absence of non radiative recombination centers in these QWs. The nonpolar structures were doped using nitrogen a as potential acceptor in ZnO. A Nitrogen concentration up to 1020 cm-3 can be incorporated without deteriorating the structural quality. We demonstrate that the nitrogen incorporation gives rise to acceptor states observed in PL in agreement with the electrical measurements (180meV and 480meV). Finally, we will present the first electroluminescence from a non polar QW.

Fecha: viernes, 4 de enero de 2013
Hora: 12:00 hora
Lugar: Sala B-103. Edificio García Redondo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Implementation of a Deep Level Transient Spectroscopy System
Ponente: Alejandro Kurtz de Griñó
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación, Universidad Politécnica
Resumen:
Lectura de Proyecto Fin de Carrera

Fecha: viernes, 14 de diciembre de 2012
Hora: 16:00 hora
Lugar: Salón de Grados del Edificio Sanz Mancebo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Generación de luz blanca eficiente con nanoestructuras semiconductoras
Ponente: Prof. Enrique Calleja Pardo
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación,Universidad Politécnica de Madrid
Resumen:
Se analiza en crecimiento epitaxial selectivo de nanoestructuras de InGaN mediante la técnica MBE (Molecular Beam Epitaxy) sobre substratos con máscaras de nanoagujeros de titanio. El éxito en este tipo de crecimiento depende de un balance crítico entre la difusividad de los átomos metálicos y su desorción, la rugosidad de la superficie, y la razón III/V. Se discuten diferentes aproximaciones a la generación de luz blanca de estado sólido sin utilización de fósforo conversor, como es el caso de zonas activas de InGaN en forma de: i) pozo cuántico ii) región extensa con composición fija iii) región extensa con composición gradual iv) estructura RGB (rojo-verde-azul). https://www.youtube.com/watch?v=_BjyDPnCw28

Fecha: lunes, 19 de noviembre de 2012
Hora: 9:30 hora
Lugar: Departamento de Ciencia de Materiales. E.T.S.I. de Caminos, Canales y Puertos. Universidad Politécnica de Madrid. [Cómo llegar]
 
Título: Nanostructures and their Applications
Ponente: Prof. Magnus Willander
Organismo: Department of Science and Technology, Linkoping University, Sweden
Resumen:
He will give a short background of low temperature chemical growth of several different nanostructures in several different materials and on different substrates. Their optical, electrical, mechanical and chemical properties will be discussed. Finally applications of the nanostructures for lasers, LEDs, optical detectors, chemical sensors and piezoelectrical generators will be reviewed.

Fecha: miércoles, 3 de octubre de 2012
Hora: 12.00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Atomically thin crystals: Beyond graphene
Ponente: Dr. Andrés Castellanos-Gómez
Organismo: Kavli Institute of NanoScience, TU Delft, Netherlands
Resumen:
In this talk Dr. Castellanos-Gómez will introduce and motivate the study on the fabrication and characterization of the mechanical and electrical properties of atomically thin crystals different than graphene. He will focus on Molibdenum Disulphide which is considered a case of special interest. Single-layer MoS2 is an attractive two-dimensional material that combines the mechanical flexibility of graphene with a large direct bandgap. While graphene is very interesting as a transparent electrode, its lack of a bandgap limits its usefulness in semiconducting and optoelectronic devices. Atomically thin MoS2, on the other hand, has a large intrinsic bandgap. This attractive feature has been recently employed to fabricate many devices not possible in graphene, such as field-effect transistors with high mobility and current on/off ratio, logic gates and efficient photo-transistors.

Fecha: viernes, 21 de septiembre de 2012
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Constituent Blocks of III-Nitride Microcavities Grown by Molecular Beam Epitaxy
Ponente: Zarko Gacevic/Director de tesis: Prof. Enrique Calleja Pardo
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación,Universidad Politécnica
Resumen:
In semiconductor microcavities light is confined by high reflectivity distributed Bragg reflectors whereas matter is confined by quantum wells or dots. By a proper tuning, the light and matter can be made to interact forming quasi-particles known as polaritons. The properties of microcavities are exploited for realization of ultra high spectral purity light emitting devices and nearly zero-threshold polariton lasers. This doctoral thesis deals with microcavity fabrication using III-nitride materials for applications in the violet/blue spectral range. http://www.upm.es/internacional/UPM/UPM+Channel/News/72c6465ef6748310VgnVCM10000009c7648aRCRD

Fecha: miércoles, 4 de julio de 2012
Hora: 12:00 hora
Lugar: Salón de grados, Edificio Sanz Mancebo, ETSIT-UPM [Cómo llegar]
 
Título: Novel designs for quantum computers using moving quantum dots
Ponente: Dr C. J. B. Ford
Organismo: Cavendish Laboratory, University of Cambridge, UK
Resumen:
Quantum computers have the potential to solve problems too complex for any classical computer. There are many proposed types of quantum bit (qubit), using for example, light, superconductors, semiconductors, trapped atoms or ions. It is not clear which of these has all the necessary properties (coherence, scalability etc). However, each presents technological challenges and goals that are interesting and fruitful in their own right, and tell us more about quantum mechanics and the act of measurement of quantum systems. Solid-state semiconductor-based qubits (in quantum dots) have many advantages, since they can be produced using fairly standard lithography, which potentially can be scaled to produce thousands of qubits, and electrons can be made to interact controllably with neighbouring qubits. Our particular proposal uses single-electron dots dragged along parallel channels by a surface acoustic wave. In places, adjacent dots come close so that electrons become entangled (two-qubit operations). In others, nanomagnets can rotate their spins (single-qubit operations). Readout can be by recombining the electrons with holes, to generate polarised photons. I will describe our measurements of coherent charge oscillations and of charge transfer between separated static dots.

Fecha: lunes, 25 de junio de 2012
Hora: 16:00 hora
Lugar: Sala 206-1. Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Crecimiento, fabricación y caracterización de heteroestructuras y nanocolumnas ordenadas basadas en nitruros del grupo III para aplicaciones sensoras
Ponente: Dña. Ana María Bengoechea Encabo / Director de tesis: Dr. D. Miguel Ángel Sánchez-García
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación,Universidad Politécnica
Resumen:
Lectura y Defensa de Tesis Doctoral

Fecha: viernes, 8 de junio de 2012
Hora: 12:00 hora
Lugar: SALÓN DE GRADOS-EDIFICIO A de la ETSI de Telecomunicación (UPM) [Cómo llegar]
 
Título: Semiconductor Quantum Nanostructures by Droplet Epitaxy
Ponente: Prof. Stefano Sanguinetti
Organismo: Dipartimento di Scienza dei Materiali, Università di Milano Bicocca, Italy
Resumen:
The Droplet Epitaxy (DE) is an MBE growth method which allows for the fabrication of III-V quantum nanostructures with highly designable shapes and complex morphologies. With DE it is possible to combine different nanostructures, namely quantum dots, quantum rings and quantum disks, with tunable sizes and densities, into a single multi-function nanostructure, thus allowing an unprecedented control over electronic properties. Unlike standard self-assembly techniques, DE does not rely on strain for the formation of three-dimensional crystals. DE is based on the fine control of the crystallization kinetics of pulsed deposition of III and V column elements at controlled temperatures and fluxes. Recent achievement in DE nanostructure shape manipulation and modeling will be presented.

Fecha: jueves, 7 de junio de 2012
Hora: 11:30 horas
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Transporte Dependiente de Espín en Estructuras de Magnetorresistencia Gigante con Capas Delgadas de Gadolinio
Ponente: D. Miguel Romera Rabasa /Director de Tesis: Dr. D. José Luis Prieto Martín
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación,Universidad Politécnica
Resumen:
Lectura y Defensa de Tesis Doctoral

Fecha: lunes, 21 de mayo de 2012
Hora: 12.00 hora
Lugar: Sala de Grados del Edificio A de la ETSI de Telecomunicación [Cómo llegar]
 
Título: High precision pressure sensors based on SAW devices fabricated on diamond substrates
Ponente: J.G. Rodríguez-Madrid
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación,Universidad Politécnica
Resumen:
For the last few decades surface acoustic wave devices have been used not only for wireless communication systems, but also for gas, temperature and pressure sensors due to their intrinsic energy confinement in a narrow region underneath the surface. Due to the sensitivity increases when the frequency is higher, this is one of the most important factors in the selection of a suitable substrate for SAW sensors. In order to achieve higher frequencies, either the selection of a suitable material with higher phase velocity or a smaller IDT period must be considered. Aluminium nitride (AlN) deposited on chemical vapour deposition diamond is a very attractive structure for high frequency SAW devices. The main problem of synthetic diamond is its high surface roughness that worsens the sputtered AlN quality and hence the device response. We have then analysed the influence of the surface roughness on the crystal quality of the sputtered thin AlN film and device response. Moreover, in this work we use a 20 µm thick nanocrystalline diamond free standing film, whose silicon substrate was removed by chemical etching, to fabricate high frequency SAW resonators operating in the 10-14 GHz frequency range. This structure not only allows depositing high c-axis oriented AlN due to the low surface roughness of the nucleation side, but also the membrane is free to move so it provides pressure sensitivity. A SAW based sensor pressure with a sensibility of 3 Mhz/bar has been fabricated.

Fecha: viernes, 11 de mayo de 2012
Hora: 12:00 hora
Lugar: Aula B-11. Edificio García Redondo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: An introduction to photovoltaics
Ponente: Prof. Steve A. Ringel
Organismo: The Ohio State University and Institute for Materials Research (IMR), Ohio (USA)
Resumen:
Advances in Electronic Systems Engineering (Seminar),Máster Universitario en Ingeniería de Sistemas Electrónicos,Curso 2011-2012

Fecha: martes, 17 de abril de 2012
Hora: 11:00 hora
Lugar: Salón de Grados del Edificio Sanz Mancebo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Terahertz Studies towards Fast Imaging
Ponente: Prof. H.L. Hartnagel
Organismo: Fachgruppe Mikrowellenelektronik, Institute for Microwave and Optics Technical University Darmstadt, Darmstadt, Germany
Resumen:
So far THz scanners are single component systems with mechanical scanning (piezoelectric MEMS etc). An important task is therefore to develop THz camera concepts. Given the wavelength of THz frequencies, the pixel has to have dimensions around 1mm giving with 10x10 pixels a receiver surface of around several cm. Each pixel needs a detector (either with Schottky diodes, or for direct mixing into optics corresponding schemes) and an antenna with small side lobes to prevent coupling between pixels. Illumination by THz needs significant power levels by paralleling optical mixer sources for THz generation as matrix with heat sinking strategies. A few other related research efforts of the author are also to be described.

Fecha: miércoles, 28 de marzo de 2012
Hora: 11.00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Is Graphite the best Graphene? Searching for its intrinsic transport properties
Ponente: Prof. Pablo Esquinazi
Organismo: Head of the Division of Superconductivity and Magnetism, and Dean of Studies for Physics and Meteorology, University of Leipzig, Germany nductivity and Magnetism, University of Leipzig, Germany
Resumen:
The experimental research of the last years on the properties of a single graphite layer dubbed graphene suggests that one may achieve the basis for new nanodevices. There are several experiments showing nowadays carrier mobility with values ~105cm2V-1s-1 or carrier concentrations below ~1010 cm-2 in graphene on substrates, grown on SiC or suspended. How are those values in comparison with those in the graphene layers inside graphite? Though graphite was studied systematically in the last ~70 years and scientists flooded the literature with reports on different kinds of electronic measurements, there was actually no real knowledge on the internal structure of the measured samples as well as the extraordinary sensitivity of the graphite structure to defects and their influence on transport. Recently done transport measurements in bulk as well as in mesoscopic, oriented thin graphite samples with micro-constrictions and multielectrodes indicate a mobility per graphene layer up to 100 times larger (carrier mean free path at 300K in the micrometer range) and carrier concentrations at least ~10 times smaller than the lowest measured in graphene. Furthermore, low-energy TEM characterization of graphite sub-mesoscopic structures as well as proton irradiation experiments on mesoscopic graphite samples provide evidence for the relationship between defects and measured carrier concentration. This new knowledge casts strong doubts on the relevance of the electronic band-structure and its tight binding parameters obtained in the past based on erroneous assumptions on the intrinsic properties of ideal graphite. In my talk I will shortly review and discuss old and new experimental evidence and argue that nowadays graphite appears to be a narrow gap semiconducting and multi-layer system with nearly decoupled two-dimensional graphene planes of much better quality than single isolated layers.

Fecha: miércoles, 29 de febrero de 2012
Hora: 15.00 hora
Lugar: Salón de Grados del Edificio Sanz Mancebo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Carbon Nanoelectronics for RF Applications
Ponente: Prof. Mircea Dragoman
Organismo: National Institute of Research and Development in Microtechnology (IMT) in Bucharest, Romania
Resumen:
In his talk he will focused on the application of carbon nanotubes and graphene for various RF applications such as controlled propagation, detection, multiplication and biosensing

Fecha: martes, 7 de febrero de 2012
Hora: 17:00 hora
Lugar: Sala C-206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Epitaxial metal nanocrystal-semiconductor quantum dot plasmonic nanostructures
Ponente: Adam Urbanczyk
Organismo: COBRA Research Institute, Eindhoven University of Technology
Resumen:
Certainly one of the most fascinating applications of plasmonics is in active structures like nanolasers, optical transistors and photonic switches, where a metal nanostructure is combined with single emitter, for example a semiconductor quantum dot (QD). Such hybrid nanostructures can easily be scaled to subwavelength dimensions. However, fabrication of such devices requires single-nanometer precise control of the separation of the metal nanostructure and the emitter due to the extremely strong confinement of the electromagnetic field of the surface plasmon resonance (SPR) supported by the metal nanostructures. Our approach to solve this problem is based on the self-alignment of epitaxial metal nanocrystals on near surface InAs QDs, all grown by molecular beam epitaxy (MBE). It has been demonstrated for In [1], as well as Ag nanocrystals [2], the latter metal being the material of choice for plasmonic applications, offering the lowest resistive losses. Moreover, this approach, being based on standard epitaxial growth technology, offers the possibility of integration of active plasmonic nanostructures with existing photonic and electronic semiconductor devices. In the talk I will present our latest results of the self-alignment of epitaxial Ag nanocrystals on epitaxial near surface InAs QDs grown on GaAs (100) substrates by MBE. The SPR wavelength of the Ag nanocrystals can be easily tuned over a wide range, covering the emission wavelength of the QDs. Low temperature Photoluminescence (PL) measurements reveal enhanced intensity of the emission, with lines from individual QDs being resolved.

Fecha: jueves, 26 de enero de 2012
Hora: 11:30 hora
Lugar: Sala B-103, Edificio García Redondo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Spectroscopy of droplet epitaxial GaAs nanoemitters
Ponente: Dr Marco Abbarchi
Organismo: Laboratoire Pierre Aigrain, École Normale Supérieure, CNRS (UMR 8551), Université P. et M. Curie, Université D.Diderot
Resumen:
Droplet epitaxy (DE) is a non-conventional growth technique based on molecular beam epitaxy. This method, differently from strain-induced 3-dimensional nanostructures, enables the growth of lattice-matched and strain-free selfassembled III-V nanoemitters. Thanks to the versatility of the DE, different kinds of nanostructures can be realized: quantum dots, coupled quantum dots, quantum rings, multiple concentric quantum rings, quantum disks, as well as combinations of these different shapes. Moreover, DE enables the growth on different substrates orientations (such as the (100), (311)A, (111)A) and, most importantly, it makes possible the growth of bright III-V quantum emitters on substates made of Silicon and Germanium.In this seminar I will introduce some features of growth and photoluminescence spectroscopy of single GaAs/AlGaAs DE nanostructures. In particular I will concentrate on quantum dots and rings addressing their electronic structure, fine structure and line broadening: I will show how composition, shape, geometrical anisotropy and disorder rule the optical properties and how, thanks to recent advances in the DE method, bright and sharp photoluminescence lines can be obtained in circular symmetric quantum dots. Finally I will show recent advancesin the growth of hybrid III-V/IV quantum dots.

Fecha: viernes, 16 de diciembre de 2011
Hora: 10:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: AlN - nanodiamond based MEMS and NEMS
Ponente: Prof. Vadim Lebedev
Organismo: Fraunhofer IAF, Friburgo (Alemania)
Resumen:
Future generations of MEMS require new advanced materials with significantly improved mechanical and chemical properties. Nanodiamond (ND) and AlN thin films have recently attracted much attention due to their applicability in rf and bio-medical transducer applications. AlN/ND- based microstuctures show a very good coupling efficiency, offering an essential advantage over conventional solutions combining the advanced mechanical properties, simplicity of microfabrication, chemical inertness, long life and the ability to operate in harsh environments. This allows for the realization of unique micromechanical devices, e.g. ultrasensitive robust sensors, adjustable rf components as well as strain-engineered optical MEMS. The development AlN/ND heterostructures for adjustable microlenses, rf switches and implantable piezo-generators is addressed in this talk with particular focus on high frequency applications.

Fecha: lunes, 5 de diciembre de 2011
Hora: 11:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Chemical sensing with AlGaN/GaN structures
Ponente: Prof. Volker Cimalla
Organismo: Fraunhofer IAF, Friburgo (Alemania)
Resumen:

Fecha: lunes, 5 de diciembre de 2011
Hora: 11.30 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Magnetic Hall sensors based on III-V heterostructures
Ponente: Prof. Sylvie Contreras
Organismo: Univ. Montpellier 2, Montpellier (Francia)
Resumen:
Hall sensor devices are strongly requested for fundamental, industrial and/or military applications. In our laboratory, in collaboration with ITRON-France, we have developed Hall sensors based on III-V Arsenide heterostructures for electricity metering. At high temperature (T>250°C) this type of Hall sensor as well as the usual semiconductors like Si, InSb, InAs or GaAs reach their natural thermal limits. At elevated temperature, the use of a wide band gap material like silicon carbide (SiC) or gallium nitride heterostructures is a prerequisite. With respect to SiC they offer the important advantage over the bulk material to provide a more stable carrier density. In this work, we present experimental results obtained by investigating a series of AlGaN/GaN heterostructures. It is demonstrated that these heterostructures can be used as magnetic sensors in a large temperature range (4.2-750 K) with a magnetic sensitivity close to 60 V/A/T and a small thermal drift (-7 ppm/°C)

Fecha: viernes, 28 de octubre de 2011
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Challenges of Understanding GaN HEMT Degradation and Reliability and Recent Results
Ponente: Prof. Steve A. Ringel
Organismo: The Ohio State University
Resumen:
Due to their large bandgaps, high breakdown voltages and high electron mobility, GaN High Electron Mobility Transistors (HEMTs) display extraordinary device performance making them the leading advance technology for high power RF applications. However the extreme conditions in which GaN HEMTs are operated challenge both the limits of GaN material properties and also challenge our understanding of the nature in which GaN devices can degrade. This presentation covers recent advances made toward observing defects and bandgap states that are associated with the causes of GaN HEMT degradation under both RF and DC stressing. Specifically, the presentation describes how we have taken a materials science defect characterization method known as Deep Level Optical Spectroscopy and adapted it to be useful to characterize defects and their behavior in actual GaN HEMTs that have been stressed in various fashions. Direct relationships are established between specific traps and HEMT degradation mechanisms, for both MBE and MOCVD devices, with different behaviors observed for both growth methods. This information can be used in the future to create accurate, predictive models of failure mechanisms in GaN HEMT technology for both RF and DC operating conditions.

Fecha: miércoles, 26 de octubre de 2011
Hora: 12-13 hora
Lugar: Salón de Grados , Edificio Sanz Mancebo, ETSI Telecomunicación [Cómo llegar]
 
Título: Resultados de la caracterización eléctrica de los semiconductores GaInAs, GaInNAs, InN y GaN.
Ponente: Dr. Victor Tapio Rangel Kuoppa
Organismo: Instituto de Semiconductores y Estado Solido de la Universidad Johanes Kepler, Linz, Austria
Resumen:
Los semiconductores III-V-N han atraído la atención últimamente, por su potencial para obtener anchos de banda que permitan la formación de láseres emitiendo a 1.3 y 1.55 µm, adecuados para comunicaciones por fibra óptica. En especial, en el caso de GaInNAs, una apropiada combinación de In y N permiten la formación de un cristal con la misma constante de red que el GaAs, lo que permitiría aprovechar toda la tecnología del GaAs. En el caso de InN y GaN, con anchos de banda 0.6 y 3.4 eV, respectivamente, sus aleaciones, junto con el ancho de banda de AlN (6 eV), permitiría la formación de celdas solares que cubrirían prácticamente todo el espectro de luz solar. Por lo anterior, es importante obtener las propiedades eléctricas de estos materiales. En esta charla se comentarán los resultados de la investigación que he llevado durante mi carrera profesional de la caracterización eléctrica de estos materiales.

Fecha: martes, 25 de octubre de 2011
Hora: 16:00 hora
Lugar: Salón de Grados. Edificio Sanz Mancebo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: New strategy in nanoparticle fabrication. Generation of nanoclusters with adjustable size and chemical composition in UHV
Ponente: Dra. Lidia Martínez
Organismo: Instituto de Ciencia de Materiales de Madrid
Resumen:
We present a new design of nanocluster source based on the sputtering gas aggregation source that allows the generation of nanoparticles with controllable and tunable chemical composition while keeping the control of the cluster size. The new design of Ion Cluster Source called Multiple Ion Cluster Source (MICS) enhances the potentialities of the standard Ion Cluster Sources were the modification of the nanoparticles stoichiometry implies the brake of the vacuum and the replacement of the target material. We will present some examples of applications of the systems grown using the MICS.

Fecha: jueves, 15 de septiembre de 2011
Hora: 12:30 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Optoelectronic devices based on oxide and arsenide compound semiconductors
Ponente: Dr. Kenji Yamamoto
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación,Universidad Politécnica
Resumen:
Today optoelectronic devices such as light-emitting diodes (LEDs), laser diodes (LDs), and photodetector diodes (PDs), are widely used in large-screen light sources, in optical pickups, and in optical fiber communications. Those devices are composed of various semiconductors which posses a band-gap energy related to a desired emission/ detection wavelength. In this seminar, oxide-based LEDs and arsenide-based PDs will be described. I will also talk on my experience in Shizuoka University (Japan), where I graduated.

Fecha: martes, 12 de abril de 2011
Hora: 18:00 hora
Lugar: Salón de Grados del Edificio Sanz Mancebo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: III-Nitride FETs on Nitride Substrates
Ponente: Prof. Masaaki Kuzuhara
Organismo: University of Fukui (Japan)
Resumen:
III-nitride electron devices are attracting considerable attention for future wireless communication and power electronics applications. This seminar will cover a brief overview on the state-of-the-art performance of AlGaN/GaN heterojunction FETs. Focus is on the future perspectives of new III-nitride device structures for improved device performance.

Fecha: lunes, 14 de marzo de 2011
Hora: 16:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación, UPM. [Cómo llegar]
 
Título: Primeras Jornadas Científicas CAMPUS EXCELENCIA INTERNACIONAL MONCLOA Cluster materiales para el futuro
Ponente: Profesor D. Claudio Aroca
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación,Universidad Politécnica
Resumen:
Presentación de los Grupos de Investigación del ISOM (Grupo de Dispositivos de Semiconductores del ISOM y Grupo de Dispositivos Magnéticos del ISOM)

Fecha: miércoles, 23 de febrero de 2011
Hora: 19:20 hora
Lugar: E.T.S. Ingenieros de Caminos, Canales y Puertos de Madrid (UPM) [Cómo llegar]
 
Título: El grafeno y sus propiedades únicas.
Ponente: Prof. Dr. Francisco Guinea
Organismo: Instituto de Ciencia de Materiales de Madrid, CSIC
Resumen:
El grafeno es una membrana de un átomo de espesor. Se trata de un nuevo material que presenta muchas propiedades especiales, que no se encuentran en otros sistemas. Se describirán algunas de estas propiedades, así como las investigaciones en curso para entender su origen y posibles aplicaciones.

Fecha: martes, 8 de febrero de 2011
Hora: 16.00 hora
Lugar: Salón de Grados del Edificio A de la ETSIT. [Cómo llegar]
 
Título: Seminario sobre Seguridad en el ISOM
Ponente: Prof. Claudio Aroca
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación,Universidad Politécnica
Resumen:

Fecha: martes, 21 de diciembre de 2010
Hora: 10.30 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Diseño de materiales magnéticos a la carta y su aplicación a dispositivos magnéticos
Ponente: Prof. Claudio Aroca
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), y Departamento de Física Aplicada de la E.T.S.I.T de la UPM
Resumen:
The possibility of tailoring the properties of a magnetic material to obtain the best performance in a given application has been traditionally an unreachable dream. Until recently the main research effort was dedicated to obtain specific materials for a wide range of applications i.e. soft magnetic materials, hard magnetic material, recording media, etc.. These materials were used in different devices with small modifications because their magnetic behavior was implicit to its composition or crystalline structure Amorphous and nano crystalline materials were a very important change because they were like an unwritten book and its anisotropy and its soft or hard magnetic behavior was easily controlled by using different thermal treatments. Now a days the magnetic material seems more like an additional component of an integrated device. It is just an additional process, similar to the inclusion of a conductive path or the inclusion of transistors. Actually the magnetic anisotropy is almost perfectly controlled and the use of high vacuum and clean room techniques allows the growing of multilayer materials with excellent interfaces and the exchange interaction is a new element of design. In the talk we will make a revision of the different techniques to perform the magnetic materials tailoring and its application to some devices or to solve some technical problems

Fecha: lunes, 22 de noviembre de 2010
Hora: 9:30 horas
Lugar: Departamento de Ciencia de Materiales. ETSI Caminos, Canales y Puertos de la UPM [Cómo llegar]
 
Título: Nanohilos de Silicio: Fabricación y Aplicaciones
Ponente: Dr. Javier Martínez Rodrigo
Organismo: C.S.I.C.- Instituto de Microelectrónica de Madrid
Resumen:

Fecha: viernes, 19 de noviembre de 2010
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Optical MEMS Technologies For Multi-Spectral Infrared Sensors and Arrays
Ponente: Prof. Lorenzo Faraone, FAA, FTSE, SMIEEE IEEE-EDS Distinguished Lecturer
Organismo: Microelectronics Research Group, The University of Western, Australia
Resumen:
State-of-the-art infrared (IR) focal plane array (FPA) technologies aim to improve the performance of IR imaging systems by reducing cooling requirements and/or adding so-called multi-colour capability, which allows on-pixel information to be gathered from two or more spectral regions. Spectral information allows improved target recognition and reduced false alarm rates in military applications, and accurate temperature determination in civilian applications. It has been recognised, however, that in order to extract spectroscopic or detailed information from a cluttered image, much better spectral resolution is required than can be afforded by such multi-colour systems. A number of research programs are aiming to address this issue by obtaining significantly better spectral resolution by developing technologies for the integration of individual tuneable optical filters on each pixel of a detector array. The approach chosen by The Microelectronics Research Group (MRG) is to develop a micro-electromechanical systems (MEMS) technology that is compatible with large format two-dimensional infrared focal plane arrays. Such a device structure consists of an electrostatically controlled Fabry-Perot filter that is integrated optically ahead of the individual detectors in an array. The demonstration of this technology has involved major advances in the deposition of silicon nitride (SiNx) thin films for mirror support structures, and the development of new Bragg mirror designs. This presentation will outline the basic concept of the approach, modelling results giving predicted device performance, several of the major hurdles to be overcome in this technology, results related to control of film stresses in SiNx films, as well as demonstration of an integrated microspectrometer technology comprising a MEMS filter and an infrared sensor capable of low-voltage tuning across the SWIR and MWIR wavelength bands

Fecha: lunes, 20 de septiembre de 2010
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Synthesis and Characterization of quasi-single-crystal ZnO films on ZnO coated Silicon Substrates
Ponente: Verónica Gao Zhan
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación,Universidad Politécnica
Resumen:

Fecha: lunes, 19 de julio de 2010
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Synchronization of spin-transfer nano-oscilators
Ponente: Julie Grollier
Organismo: Unité Mixte de Physique CNRS-THALES (del grupo de Albert Fert, Nobel 2007).
Resumen:
Presentación de algunos de sus resultados en transferencia de espín.

Fecha: jueves, 1 de julio de 2010
Hora: 12:00 hora
Lugar: Sala de Grados, Edificio Sanz Mancebo, ETSI Telecomunicación. [Cómo llegar]
 
Título: Técnicas de caracterización de materiales aplicadas al nitruro de aluminio
Ponente: D. José Capilla Osorio
Organismo: Grupo GMME, Departamento de Tecnología Electrónica de la E.T.S.I. Telecomunicación,Universidad Politécnica
Resumen:
Para la caracterización de la cristalinidad de materiales se utiliza típicamente la Difracción de Rayos X (XRD). En esta charla se presenta la Espectrometría de Infrarrojos por transformada de Fourier (FT-IR) como una técnica complementaria en la evaluación de la calidad cristalina. El material sobre el que se mostrarán las técnicas es el nitruro de aluminio (AlN). Dada la piezoelectricidad del material elegido, se presentará también la fabricación de dispositivos BAW como medio para obtener el coeficiente de acoplo electromecánico del material.

Fecha: jueves, 27 de mayo de 2010
Hora: 12:30 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Procesado y caracterización de nanohilos de ZnO crecidos MOCVD
Ponente: D. Manuel López Ponce
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación,Universidad Politécnica
Resumen:
El ZnO posee unas propiedades óptimas para la detección de luz UV y de gases. Además de poseer una alta energía de enlace del excitón tiene gran facilidad para obtener nanoestructuras. Los nanohilos de ZnO poseen una superficie altamente sensible al medio en el que se encuentran y debido a su alta relación superficie-volumen, se convierten en muy buenos candidatos para la fabricación de nanodispositivos. En este proyecto se ha desarrollado una técnica de procesado para el contacto de nanohilos individuales para posteriormente analizar sus propiedades de transporte.

Fecha: jueves, 27 de mayo de 2010
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Self-heating effects in AlGan/GaN HEMTs at high temperature
Ponente: Doña Sara Martín
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación,Universidad Politécnica
Resumen:
The self-heating effects in AlGaN/GaN HEMTs grown on sapphire and SiC substrates have been evaluated for operation temperatures from 300 K to 500 K. Main DC parameters, such as ID or gm, show reductions as temperature rises. Pulsed measurements with different pulse widths have been performed in order to estimate the channel temperature as a function of the output power by varying the ambient temperature of the HEMTs. The results obtained from this simple method are in good agreement with simulations of the channel temperature.

Fecha: viernes, 14 de mayo de 2010
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: The influence of the substrate roughness on the c-axis orientation of AlN/DIAMOND thin films
Ponente: D. Juan G. Rodríguez
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación, Universidad Politécnica
Resumen:
The AlN/Diamond structure is an attractive combination for SAW devices and its application at high frequencies. In this work, the crystallographic properties of reactively sputtered AlN thin films synthesized on different diamond substrates have been studied. Polished micro and nano-crystalline diamond substrates, with a roughness of 1.38 nm (rms) and 10.71 nm (rms) respectively, were used to deposit ∼1 μm of AlN under equal sputtering conditions. The discharge power was varied from 400W to 800W with all other parameters fixed. For the smoother substrate, the FWHM of the rocking curve of the (002) AlN peak varies from 3.8° to 2.3° with increasing power. For the roughest diamond, the FWHM varies from 10.9° to 27.1°. SAW devices are being developed on the piezoelectric layers.

Fecha: viernes, 14 de mayo de 2010
Hora: 12:30 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Spectrum Optimized Solar Cells and Green Light Emitters Using Engineered Si Substrates
Ponente: Prof. Steven A. Ringel
Organismo: Ohio State University and Institute for Materials Research (IMR)
Resumen:

Fecha: viernes, 7 de mayo de 2010
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Diamond and Self-heating in AlGaN-GaN HEMTs
Ponente: Dr. Marko Tadjer
Organismo: U.S. Naval Research Laboratory and University of Maryland
Resumen:
The extremely high thermal conductivity and mechanical hardness would make diamond the natural choice for device substrates when large area wafer production becomes possible. Until this milestone is achieved, people could utilize nanocrystalline diamond (NCD) thin films grown by metal organic chemical vapor deposition (MOCVD). A topside thermal contact could be pivotal for providing stable device characteristics in the high power, high temperature, and high switching frequency device operating regime that next-generation power converter circuits will mandate. This work explores thermal benefits offered by NCD films to improve the thermal profile of AlGaN/GaN high electron mobility transistors (HEMTs). Reduction of self-heating effects by integrating NCD thin films near the device channel is presented. The NCD layers provide a high thermal conductivity path for the reduction of hot electron dispersion, a phenomenon caused by self-heating and detrimental to the reliable operation of GaN devices in power switching circuits.

Fecha: viernes, 30 de abril de 2010
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: New trends in exchange bias in sputtered polycrystalline films
Ponente: Professor Kevin O' Grady
Organismo: University of York
Resumen:
The phenomenon of exchange bias has remained something of a mystery since it was first discovered in core shell particles in 1956 [1]. Over the subsequent years many different models have been attempted to try and explain this effect most of which agree with some experimental data that can be found in the literature. However no single theory has ever been able to put a theoretical line consistently through data for different systems. In this lecture the reason for our inability to explain exchange bias will be reviewed. Subsequently a new paradigm to explain exchange bias in sputtered polycrystalline films will be presented. This new paradigm is based on an original granular model due to Falcomer and Charap [2]. The basis of the new paradigm is that very careful thermal and magnetic cycling is required to ensure that the order in the antiferromagnetic grains is controlled carefully. Without such careful control reproducible data cannot be obtained. These measurement procedures which are time consuming and complex, we refer to as the York Protocol and have been developed over the last 9 years. It will be shown that using the York Protocol and an extension of the former granular model, effects such as the film thickness dependence and grain size dependence of exchange bias can be fully explained with an excellent fit between theory and experiment [3]. The York Protocol also allows for the measurement of the anisotropy constant of antiferromagnetic grains [4]. The above model allows for an understanding of the behaviour of the individual AF grains in detail. Since the behaviour of the "bulk" of the antiferromagnetic grains is now known preliminary data describing the behaviour of the interface spins can now be distinguished from the behaviour of the bulk. Possible mechanisms for the behaviour of the interfaces themselves will also be presented.

Fecha: lunes, 12 de abril de 2010
Hora: 12:00 hora
Lugar: Aula Magna. Edificio Sanz Mancebo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Recent progress in GaN-based nanocolumns and related technology
Ponente: Professor Katsumi Kishino
Organismo: Sophia University Tokyo, Japan
Resumen:
The Ti-mask selective-area growth (SAG) of GaN nanocolumns was performed at the growth temperature of 900°C, while decreasing the supplied nitrogen flow rate (QN2) from 3.5 to 0.5 sccm. Highly uniform arrays of GaN nanocolumns were demonstrated. At low QN2, both the desorption and diffusion of Ga from/on the nitrided Ti mask were accelerated, which sufficiently suppressed the crystal nucleation on the Ti-mask surface, and hence the SAG of the GaN nanocolumns was achieved even when the spacing between the nanocolumns was several hundred nm. The enhancement of Ga desorption with decreasing QN2 brought about a reduction in the growth rate of GaN nanocolumns from 1.05 to 0.15mm/h. The lateral growth rate of the GaN nanocolumns rapidly increased above the critical QN2 value of 1.5 sccm and became 45 nm/h at QN2 of 3.5 sccm. For low QN2 values less than 1.5 sccm, the lateral growth rate became sufficiently low, approximately 8 nm/h; this contributes to well-controlled SAG of GaN, where the underlying nanomask patterns are well traced.

Fecha: lunes, 22 de marzo de 2010
Hora: 16:30 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Nanostructural Evolution in Materials for Use in Ferrofluids and Polymeric Nanocomposite Systems for Biomedical Applications.
Ponente: Professor Michael E. McHenry
Organismo: Carnegie Mellon University. Materials Science and Engineering
Resumen:
Important to many applications of magnetic nanoparticles (MNPs) is the high frequency switching and power absorption of air stable materials. The incorporation of water in ferrous minerals and suspension of ferrous nanoparticles in aqueous solutions has important implications for life on earth and answering questions as to extraterrestrial life. The observations of ferrous nanostructures in terrestrial biomagnetism will be reviewed. Parallels between minerals important for biological functions on earth and in answering questions as to extraterrestrial life, e.g. on Mars will be discussed. CMU research in synthesizing MNPs amenable to functionalization for applications aqueous magnetic fluids (ferrofluids) make them attractive for biomedical applications and their incorporation into polymer nanocomposites. For example, the efficient point source heating of metallic nanoparticles can be exploited for thermoablative cancer therapies and to tag and change the shape of tissue scaffolds important to regenerative medicine. Biomagnetic applications are actively pursued by CMU Materials Science and Engineering faculty in providing research and design projects to a growing number of students who opt to pursue a double major with biomedical engineering (BME). This talk will discuss research addressing biomedical applications of FeCo/(Fe,Co)3O4 core shell nanostructures. The potential importance of these materials in uses in biomedical applications will be discussed with illustrations of ferrofluid, ferrogel and MNP/polymer nanocomposites. Ferrogels (cross-linked polymers loaded with magnetic particles) are exciting smart materials because of their magnetic shape memory effects. They use magnetic particle chaining in a polymer matrix in response to an applied magnetic field to change the mechanical state of the nanocomposites. Depending on the type of application, the mechanical or thermal response of a magnetic particle-reinforced polymer composite can be tailored as a function of combined applied DC and AC magnetic fields. Efforts to sense these MNP′s in-situ will also be discussed.

Fecha: viernes, 5 de marzo de 2010
Hora: 12:00 hora
Lugar: Salón de Grados del Edificio Sanz Mancebo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Source and Drain Resistances Behaviour as a Function of Temperature and Drain Current in AlGaN/GaN HEMTs
Ponente: Roberto Cuerdo Bragado
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación, Universidad Politécnica
Resumen:
The behaviour of source and drain resistances (RS and RD) in AlGaN/GaN HEMTs is studied for a wide range of drain currents at ambient temperatures from 150 K to 500 K. Both parasitic resistances show an important increase as temperature rises, directly related to the reduction in the electron mobility. High drain currents also provoke a non-linear increment of RS and RD, once the space-charge limited current is exceeded. Both temperature and drain current mechanisms have been modeled together by means of a simple equation, with good agreement between simulations and measurements. Non-linear RS and RD allow a more accurate extraction of the intrinsic parameters, especially in the high drain currents range. The use of variable parasitic resistances instead of the usually assumed constant values reveals higher gm,int and Cgs. This study provides useful information for the design of HEMTs working at high powers and high temperatures.

Fecha: viernes, 26 de febrero de 2010
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Defect spectroscopy with positrons: what can we learn on III-nitrides and other compound semiconductors?
Ponente: Dr. Filip Tuomisto
Organismo: Positron research group leader Academy Research Fellow, Docent Department of Applied Physics Aalto University Finland
Resumen:
Point and extended defects present in the lattice determine many of the crucial properties of semiconductors, such as the efficiency of electron-hole production through optical excitation and the diffusion length of carriers. I will introduce a method called positron annihilation spectroscopy and how it is used to identify vacancy defects in compound semiconductors, specifically in III-nitrides. It is based on the special property of positrons: they can get trapped at negative and neutral vacancy defects, and at negatively charged non-open volume defects given the temperature is low enough. The trapping of positrons at these defects is observed as well-defined changes in the positron-electron annihilation radiation. The combination of positron lifetime and Doppler broadening techniques with theoretical calculations provides the means to deduce both the identities and the concentrations of the vacancies in the materials. Performing measurements as a function of temperature gives information on the charge states of the detected defects. The III-sublattice vacancies are identified as common defects in all the III-nitrides, and they compensate donors either by forming vacancy-impurity complexes or by providing deep states for electrons. In some cases also N vacancies can be observed. Filip Tuomisto received his doctoral degree from the Department of Engineering Physics and Mathematics, Helsinki University of Technology (TKK) in 2005. He is currently an Academy Research Fellow at Aalto University, where he leads the positron research group (presently 6 PhD students, 2 post-docs). Dr. Tuomisto has published more than 90 scientific papers. His research interests include physics of positrons in matter, defect spectroscopy of semiconductors and metals, and semiconductor optoelectronics.

Fecha: martes, 16 de febrero de 2010
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Multiplicadores de frecuencia MMIC para ondas milimétricas
Ponente: Dra. Yolanda Campos
Organismo: Universidad de Extremadura
Resumen:
La explotación del rango de las ondas milimétricas está experimentando un desarrollo creciente en los últimos años para dar soporte a aplicaciones muy diversas, tanto en el campo de las comunicaciones como de los sistemas radar. Uno de los problemas más críticos en el diseño de muchos de estos sistemas es la generación de la señal, con frecuencia sometida a especificaciones estrictas de ruido de fase y de estabilidad de frecuencia. Una solución atractiva para la realización de una fuente de señal a estas elevadas frecuencias consiste en combinar un oscilador a una frecuencia menor con uno o varios multiplicadores de frecuencia. Se presentará el diseño óptimo y los resultados experimentales de diversos multiplicadores de frecuencia MMIC, con frecuencias de salida en las bandas V, W, D y G, basados en dos procesos: PHEMT de AlGaAs/InGaAs/GaAs y MHEMT de InAlAs/InGaAs/GaAs. Todos ellos han sido realizados en tecnología coplanar.

Fecha: viernes, 12 de febrero de 2010
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Systematic Study of Internal Quantum Efficiency Mechanisms in III-Nitride Quantum Dots
Ponente: Zarko Gacevic
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación,Universidad Politécnica
Resumen:
Luminescence properties of InGaN light emitting diodes, found to be surprisingly lowly affected by the presence of high dislocations density (~109 cm-2), led to strong controversy over its light emission mechanisms. In mid 1990s it was widely speculated that this uncommon behaviour is due to strong potential fluctuations induced by composition and/or thickness fluctuations of active InGaN layers. Strongly localized in this quantum dot like regions, carriers can no longer diffuse toward non-radiative recombination centres. As response to this early evidence, in late 1990s, several groups reported on controlled fabrication of "true" III-nitride quantum dots (QDs). Over the last decade, many papers have reported on superior luminescence properties of III-nitride QDs over their quantum wells counterparts. However, there is huge dispersion in their reported internal quantum efficiencies and strong controversy over explanation of significant decrease in their optical performance with rising temperature. The aim of the work presented here is to assess non-radiative processes in polar GaN/AlN and InGaN/GaN QDs making use of temperature dependent photoluminescence. The experimental data that have been obtained are interpreted within generation-diffusion-recombination model.

Fecha: viernes, 22 de enero de 2010
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: High responsivity and internal gain mechanisms in Au-ZnMgO Schottky photodiodes
Ponente: Gema Tabares Jiménez
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación,Universidad Politécnica
Resumen:
Schottky photodiodes based on Au-ZnMgO/sapphire are demonstrated covering the spectral region from 3.35 to 3.48 eV, with UV/VIS rejection ratios up to ~105 and responsivities as high as 185 A/W. Both the rejection ratio and the responsivity are shown to be largely enhanced by the presence of an internal gain mechanism, by which a very high concentration of trapped electrons at an Ev+280 meV deep level is released upon illumination. This causes a large increase in the tunnel current through the Schottky barrier, yielding internal gains that are a function of the incident photon flux.

Fecha: viernes, 15 de enero de 2010
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Aspectos estructurales, deformación y superficies en relación con la fiabilidad de transistores de alta movilidad electrónicas basados en heteroestructuras de AlGaN/GaN
Ponente: Fernando González-Posada Flores
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación,Universidad Politécnica
Resumen:
La tecnología de nitruros es actualmente la más prometedora para la fabricación de dispositivos eléctricos de alta eficiencia en potencia a altas frecuencias y temperaturas, presentando un alto valor de voltaje de ruptura, aunque sus posibilidades están todavía por debajo de las expectativas teóricas. Inicialmente, el interés de esta tecnología se focalizó en aplicaciones militares para microondas, pero en la actualidad los transistores de alta movilidad electrónicas (HEMT) se han centrado en las comunicaciones para radiofrecuencia civiles, así como en otros sectores de electrónica de potencia. La comercialización ha hecho crecer el número de estudios relacionados con la fiabilidad, y consecuentemente, de mecanismos de fallo y degradación, para un mejor entendimiento de la física subyacente. Recientemente, en el caso de los nitruros del grupo III, la influencia de la distribución del campo eléctrico, la densidad de carga en la superficie y los efectos piezoeléctricos han cobrado relevancia en relación con la fiabilidad. En este sentido, se presenta una caracterización estructural, eléctrica y de la superficie, amplia y detallada, en múltiples heteroestructuras de AlGaN/GaN crecidas sobre sustratos diferentes (SiC, zafiro y silicio) por técnicas de crecimiento epitaxial (MBE y MOVPE) que proporcionan resultados similares. El conocimiento de la heteroestructura es fundamental para realizar simulaciones de los principales parámetros y propiedades de interés como los campos de polarización, la densidad de carga en el canal y los mecanismos de dispersión, que afectan al transporte eléctrico en las heteroestructuras y, en cualquier caso, sobre las capacidades teóricas finales de los dispositivos HEMT fabricados. La calidad cristalina de las heteroestructuras se evaluó mediante diferentes técnicas estructurales, concretamente XRD e IBA. Por otra parte, la superficie del AlGaN se analizó cualitativamente y cuantitativamente mediante XPS y AFM. Se presentan estudios concretos sobre la incorporación de aluminio en la barrera del AlGaN, la influencia en el crecimiento de las heteroestructuras de capas de adaptación y espaciadora basadas en AlN, y la presencia de hidrógeno en las heteroestructuras de AlGaN/GaN. Así mismo, se realizó un estudio detallado de la superficie de AlGaN mediante XPS, (a) después de tratamientos independientes, extraídos de pasos concretos de la fabricación de dispositivos HEMT, en relación con una superficie homogénea de referencia, sin ningún tratamiento previo; (b) sobre cuatro obleas distintas, crecidas sobre SiC, zafiro y Si, con técnicas de crecimiento similares (MBE y MOVPE) a lo largo del procesado HEMT y (c) en tres obleas similares crecidas sobre zafiro en un MOVPE con tres tratamientos previos de la superficie, basados en limpiezas orgánicas, plasma de N2 y aleados térmicos, en relación con medidas eléctricas con una sonda de Hg antes de procesar y en diodos procesados en las heteroestructuras. La conclusión principal extraída es la presencia de contaminaciones (carbono y oxígeno) en la superficie de las heteroestructuras HEMT durante el procesado, que se quedan atrapadas en las intercaras con metalizaciones y pasivantes. Se presentan diferentes métodos y combinaciones de tratamientos de la superficie para reducir la contaminación en la superficie de las heteroestructuras y en las intercaras fruto del procesado. La modificación de la superficie, mediante la limpieza de estas contaminaciones parece influir en las características del canal de electrones, responsable último del rendimiento del transistor procesado. En relación con los efectos piezoeléctricos, se han realizado estudios de estrés bajo altos campos eléctricos en transistores HEMT funcionando en corte. La degradación observada es de naturaleza cuasi-permanente, pero no parece estar relacionada con efectos piezoeléctricos sino con atrapamiento/desatrapamiento de portadores en defectos de las heteroestructuras y con la tecnología del procesado. Finalmente, se han analizado los efectos del procesado sobre las propiedades eléctricas y mecánicas de las heteroestructuras de los HEMT. Específicamente, el estado de deformación de las capas de la heteroestructura de AlGaN/GaN se ha estudiado a lo largo de diferentes pasos del procesado y las concentraciones del canal de portadores en la intercara en transistores y dispositivos de prueba. Estructuralmente, se observan ligeras modificaciones en el estado de deformación de las capas de la heteroestructura y, eléctricamente, reducciones de carga considerables en los transistores HEMT fabricados. En conclusión, se apunta que el mecanismo de fallo responsable de estas degradaciones en los transistores HEMT parece ser la modificación de la superficie del AlGaN, pues las degradaciones que involucran los efectos piezoeléctricos parecen ser de menor orden.

Fecha: viernes, 18 de diciembre de 2009
Hora: 11:00 hora
Lugar: Salón de Grados del Edificio Sanz Mancebo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Diseño, crecimiento, caracterización y fabricación de detectores de luz ultravioleta y visible basados en pozos cuánticos de nitruros del grupo III
Ponente: Juan Pereiro Viterbo
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación, Universidad Politécnica
Resumen:
The aim of this PhD thesis is the design, growth, fabrication and characterization of photodetectors based on III-N multiple quantum well structures for UV and VIS light. This report summarizes the work carried out on (Al,In,Ga)N bulk layers and multiple quantum well (MQW) heterostructures growth by plasma assisted molecular beam epitaxy. The studies on InGaN growth culminate in the development of a universal diagram which describes the growth mode and the In content of the alloy as a function of the growth conditions (In flux, N flux and substrate temperature). A complete characterization of the InGaN bulk layers has been carried out in order to understand the problems related to this alloy. Phase separation, electron accumulation at the surface, localization or In-N bond decomposition have been studied. The behaviour of these properties as a function of In content were analysed, different growth techniques were compared and the origin of each of them was assessed. These InGaN intrinsic problems are harmful for photodetector performance. Solutions in order to overcome these problems have been proposed, and specific structures, based on InGaN, have been designed, grown and fabricated. Metal-insulator-semiconductor structures, metal-semiconductor structures on p-type InGaN:Mg and MQW based photodetectors were examined in order to achieve good rectifying contacts on this ternary and to improve photodetector response in photovoltaic mode. Before the beginning of the PhD, not much work had been carried out on the development of MQW based photodetectors. This investigation has faced several problems related with basic design of the appropriate MQW structures for photodetection. It has been shown that for ternary nitrides, especially for InGaN, MQW structures solve most of the photodetector problems related to the intrinsic properties of the material that have been mentioned in previous paragraphs. New device designs based on InGaN/GaN and GaN/AlGaN MQW structures, devised to maximize UV and VIS photodetector response, are shown. These simple design rules improve photodiode responsivity up to 3 orders of magnitude. Moreover, InGaN / GaN MQW photodetectors which improve the performance of commercial Si based photodiodes at temperatures above 130°C are shown. III-N MQW structures show very high piezoelectric fields. First steps in order to use these fields to improve device performance are reported. It is shown how the proper design of the structures can allow us to increase photocarrier collection efficiency or to achieve photovoltaic response in apparently symmetric structures, just taking advantage of piezoelectric fields. Most of the work carried out during this PhD was comprised in the GaNano european project and in the Futursen project, funded by the European Union and the Comunidad Autónoma de Madrid, respectively. Both projects are aimed at the fabrication of fluorescence sensors for biological analysis of samples in aqueous solution. InGaN / GaN MQW based photodetectors and Schottky barrier photodiodes based on p-type InGaN:Mg were adapted for fluorescence measurements. The feasibility of performing fluorescence experiments using commercial fluorophores, such as Alexa Fluor or Pacific blue, has been demonstrated. This fluorophores allow the detection of nucleic acids or proteins in aqueous solutions. All the project objectives faced during this PhD thesis were fulfilled.

Fecha: viernes, 11 de diciembre de 2009
Hora: 12:00 hora
Lugar: Salón de Actos, Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Advanced Measurements-Signal Integrity... and more
Ponente: Miguel del Pie
Organismo: LeCroy
Resumen:
Module 3: Advanced Analysis for High Speed Serial Data Stream, Module 4: Real-Time Acquisition from DC up to 30 GHz and 80 GS/s, Module 5: "Sampling" and "Real-Time" Oscilloscopes

Fecha: martes, 22 de septiembre de 2009
Hora: 10:00 hora
Lugar: A-129, Edificio A, ETS Ingenieros de Telecomunicación [Cómo llegar]
 
Título: Temperature Effects during the Growth of In-rich InGaN Films by Plasma-Assisted Molecular Beam Epitaxy
Ponente: Jacqueline L. Hall
Organismo: School of Physics & Astronomy, Univ. of Nottingham, Nottingham
Resumen:
In-rich InGaN has potential applications for a number of devices. Growth of high quality structures however, requires close control of the growth parameters; namely growth temperature and composition. Since InN is a narrow bandgap material, some rise in temperature is, in most cases, expected during its growth. Due to the relatively low decomposition temperature of InN, accurate temperature control is a crucial factor in the growth process. By growing on GaAs substrates, we are able to utilise the kSA BandiT system and determine quantitatively, the rise in temperature during growth, as a function of In composition. InGaN samples have been grown by plasma-assisted molecular beam epitaxy across the entire composition range from InN to GaN. The composition was achieved by limiting the Ga:N ratio and adjusting the In flux to achieve stoichiometry and checked ex-situ with X-ray studies. Films grown under In-rich conditions were found to experience a rapid rise in temperature immediately following the start of growth; in some cases over 100oC in less than 1.5 mins.

Fecha: miércoles, 8 de julio de 2009
Hora: 12:00 hora
Lugar: B-223, Edificio B, ETSI de Telecomunicación [Cómo llegar]
 
Título: 3-Dimensional Microstructures in GaN Fabricated Using Sacrificial AlInN Layers
Ponente: Dr. Ian Watson
Organismo: Institute of Photonics, University of Strathclyde, Glasgow, U.K.
Resumen:
The ternary alloy AlInN is attracting growing interest in the III-nitride semiconductor community, which can be traced back to a report on high-quality AlInN-GaN Bragg mirrors from EPFL researchers in 2003 [1]. The ternary alloy can be lattice matched to GaN on the wurtzite-phase basal plane at an AlInN fraction of ~17% [2]. There are major differences in properties between GaN and lattice-matched AlInN, and this talk will focus on microfabrication routes exploiting differential chemical reactivity. More specifically, the fabrication of 3-dimensional microstructures by selective lateral etching of buried AlInN layers from custom-grown epitaxial structures will be discussed. Here the AlInN functions as a sacrificial layer, as used widely in established MEMS and MOEMS fabrication routes in other semiconductor materials families. One type of GaN microstructure to be discussed in detail comprise doubly supported microbridges of conductive silicon-doped GaN [3]. The dc electrical characteristics of these have been investigated to demonstrate the scope for electrostatic and/or Lorentz force actuation in similar structures. A second example involves growth of epistructures with 2 or 3 AlInN layers, which could be etched away to create air-gap vertical Bragg mirror structures. Microreflectivity measurements on the fabricated microstructures indicate high-reflectivity stop-bands with profiles close to transfer matrix simulations, and a maximum measured reflectivity in the microstructures of up to 60%. [1] J.-F. Carlin, M. Ilegems, Appl. Phys. Lett., 83, 668 (2003) [2] K. Lorenz et al, Phys. Rev. Lett., 97, 085501 92006) [3] C. Xiong et al, Appl. Phys. A, 96, 495 (2009)

Fecha: viernes, 26 de junio de 2009
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación [Cómo llegar]
 
Título: Centro de Investigación Experimental en Aplicaciones y Servicios de Inteligencia Ambiental
Ponente: Abelardo León González
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación, Universidad Politécnica
Resumen:
La Misión del Centro de Investigación en Aplicaciones y Servicios de Inteligencia Ambiental (CIAmI) es la de constituir un Grupo de Excelencia de carácter Nacional e Internacional en la investigación y desarrollo de laInteligencia Ambiental y de los aspectos relacionados con la prevención, cuidado y promoción de la salud y el bienestar de las personas, el apoyo a la inclusión social y la vida independiente, y en general para todas aquellas aplicaciones y servicios dirigidos al ciudadano, en todas las fases de la cadena de valor: la formación, la investigación teórica, la investigación experimental, el desarrollo tecnológico, y la transferencia de tecnología. La actividad del centro gira alrededor de la creación de dos laboratorios distribuidos de referencia que sirvan como un verdadero banco de pruebas para las nuevas aplicaciones y servicios avanzados que hacen un uso masivo de las TIC y que están dirigidas a la mayor parte de la población: LIVING-LAB y SMART-HOUSE.

Fecha: viernes, 19 de junio de 2009
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Controlling Chronic Diseases related to Metabolic Disorders
Ponente: Alessio Fioravanti
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación, Universidad Politécnica
Resumen:
METABO es un proyecto europeo desarrollado en el marco del 7th Framework Program que investiga los problemas relacionados con la gestión de la diabetes tanto por el paciente como por el especialista. En la actualidad, la diabetes está creciendo considerablemente en la población alcanzando cotas de prevalencia propias de una epidemia. Además, esta enfermedad es la causa de un alto porcentaje de morbilidad y mortalidad. METABO proporcionará una mejora en la gestión de la diabetes para pacientes y médicos a través de la aplicación de las últimas tecnologías. Gracias a éstas, habrá un mayor flujo de información entre ambos protagonistas, aumentando el nivel de autogestión del paciente y mejorando las terapias médicas y el diagnóstico. Por lo tanto, se puede afirmar que los resultados obtenidos gracias al proyecto METABO serán cruciales para mejorar significativamente la gestión de la diabetes. Los escenarios donde se desarrollará la investigación de METABO son los siguientes: - Cambios en el entorno. - Ejercicio físico. - Predicción de las hipoglucemias. - Falta de motivación. - Control de la inestabilidad de la diabetes. - Gestión de la co-morbilidad. El objetivo de este proyecto radica en la búsqueda de nuevas vías para mejorar la gestión clínica de la diabetes usando las últimas tecnologías disponibles, y de este modo definir los nuevos caminos dentro de los sistemas sanitarios y ayudar a los pacientes a mejorar en el autocontrol de su enfermedad.

Fecha: viernes, 19 de junio de 2009
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: Sputtering system optimization
Ponente: Juan Gabriel Rodríguez Madrid
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación, Universidad Politécnica
Resumen:
Por sus propiedades químicas, mecánicas, acústicas y ópticas el Nitruro de Aluminio (AlN) tiene un gran interés y es un candidato prometedor como material para el desarrollo de filtros de ondas acústicas superficiales (SAW), MEMS y dispositivos fotoeléctricos, entre otros. Se han utilizado diferentes técnicas para depositar AlN sobre varios sustratos, entre éstas se encuentra el CVD (Chemical Vapour Deposition), LCVD (Laser Chemical Vapour Deposition), MBE (Molecular Beam Epitaxy) y Sputtering. En la mayoría de los métodos mencionados anteriormente, la temperatura durante el proceso de crecimiento es muy alta, lo que puede degradar el sustrato. El sputtering es una técnica atractiva para el crecimiento de estas capas debido al depósito a baja temperatura, además de otras características como el relativo bajo coste, uniformidad de las capas, etc. En este seminario se explicará la técnica del Sputtering, se verán los parámetros que influyen en la calidad final de la capa crecida y de qué forma lo hacen. Se mostrarán los resultados obtenidos hasta el momento variando dichos parámetros, haciendo un análisis y comparándolo con el estado del arte con el fin de optimizar el sistema y conseguir capas de AlN orientadas en el eje c.

Fecha: viernes, 29 de mayo de 2009
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: "1.3- 1.55 µm InAs/GaAs quantum dots capped with GaAsSb: effect of the Sb content on the structural and optic"
Ponente: Dr. J.M. Ulloa Herrero
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación, Universidad Politécnica
Resumen:
A recent approach to extend the emission wavelength of InAs/GaAs quantum dots (QD) to 1.55 µm is the use of GaAsSb capping layers. Nevertheless, the physical reasons for the strong red shift obtained are still not clear. In this work, we analyze how the optical and structural properties of GaAsSb-capped InAs QDs grown by MBE evolve when the Sb content is progressively increased, and demonstrate RT photoluminescence (PL) at 1.55 µm. When the Sb content in a 5 nm thick capping layer is changed from 0 to ~25 %, two different regimes concerning the optical quality of the QDs are found. For low Sb concentrations, the PL is progressively enhanced with increasing Sb, allowing to obtain RT PL emission around 1.3 µm with improved quality compared to GaAs-capped QDs. Nevertheless, for higher Sb contents the FWHM increases rapidly with the Sb content. Cross-sectional scanning tunneling microscopy (X-STM) as well as PL measurements as a function of temperature and excitation power are used to clarify this point. On the other hand, increasing the capping thickness to 7.5 nm increases the PL wavelength with no effect on the FWHM. This is a good strategy in order to reach 1.55 µm emission with good characteristics. The observed changes are found to be partially related to structural changes in the QDs. The presence of Sb in the capping layer reduces the In-Ga intermixing during capping resulting in taller QDs due to reduced QD decomposition, as shown by X-STM and AFM measurements.

Fecha: viernes, 24 de abril de 2009
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: "Electrical and Microstructural Characteristics of Ohmic Contacts formation on AlGaN/GaN HEMT"
Ponente: M. Fátima Romero
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación,Universidad Politécnica
Resumen:
GaN and related compounds are promising semiconductors for high temperature/high power devices because of their wide-band gap which allows high breakdown voltage and high saturation current capabilities on AlGaN/GaN high electron mobility transistor (HEMT) [1-3]. Although significant progress has already been made, there are still some areas which need more research, such as ohmic contacts (drain and source) formation. Low-resistance ohmic contacts are essential for enhanced performance of HEMT, which are able to achieve high current densities, high extrinsic gain and low Joule heating loss to allow high temperature operation. Additionally, a good surface morphology and good line edge definition is required to facilitate sharp edge acuity for short channel devices [4]. With this aim, many ohmic contact structures, most of them Ti/Al-based, have been designed during the last few years to work on AlGaN/GaN devices [5-7]. Unfortunatelly, the disparate nature of t he studies carried out using different quality and doping heterostructure materials with several contact metallizations have not allowed for critical identification the role that the metal layers play in the ohmic contact formation. In addition, the effect of the metal layers and thermal cycles on the surface morphology and thermal stability of the Ti/Al-based contact was found to be critical but is not yet understood. Therefore the design of an ideal contact on AlGaN/GaN heterostructures is still lacking [8]. This work focusses on the study of Ti/Al-based ohmic contacts, in particular Ti-Al-Ti-Au metallization schemes, which are the most widely used [5-8], in order to relate the electrical properties, line edge definition, surface microstructural and depth profile compositional characteristics for several metallization schemes. Current-voltage characterization, optical microscopy (Nomarski), scanning electrón microscopy (SEM) coupled with energy dispersive x-ray spectroscopy (EDS) and Auger electron spectroscopy (AES) were used for this purpose. The thickness of the barrier layer (Ti) and the annealing temperature were found to play a very critical role in obtaining simultaneously low resistance ohmic contacts and a smooth surface with good line edge definition. A minimum contact resistance value (~0.4 Ω•mm) was achieved with a smooth line edge definition for Ti/Al/Ti/Au (20/80/50/55) nm annealed at 875ºC (Fig. 1) (Fig. 2). Similar results were obtained for three nominally i dentical wafers. These ohmic contact resistance values are of the same order of magnitude of the state of art found in the literature using a Ti-Al-Ti-Au scheme, but with a good line edge definition [5],[7-9]. From the microstructural and compositional analysis, Ga and Au distributions were found to be strongly dependent on the Al/Ti ratio from the intermediate layers and became more linked as the Al/Ti ratio decreases. Both the Ti-Al-Au distribution and Ga out-diffusion to the surface seem to play a critical role in obtaining low ohmic contact values.

Fecha: viernes, 3 de abril de 2009
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: "Growth and characterization of lattice-mismatched AlGaN/GaN and lattice-matched InAlN-GaN distributed Bragg reflectors by MBE"
Ponente: Zarko Gacevic
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación,Universidad Politécnica
Resumen:
High quality distributed Bragg reflectors (DBRs), based on nitride-compounds quarterwave layers, have huge potential for near UV - blue - green vertical cavity devices such as vertical cavity surface emitting lasers, resonant cavity light emitting diodes and Fabry-Perot modulators. Though high-reflectivity DBRs based on both AlN/GaN and AlxGa1-xN/AlyGa1-yN (for violet-blue-green and near UV applications, respectively) have been already demonstrated, the high lattice mismatch between GaN and AlN binaries remains a key problem to grow high quality III-nitride heterostructures. This mismatch results in strain accumulation leading to plastic relaxation which can be detrimental to optoelectronic devices properties. Recent interest has been focused on the growth of high quality InAlN layers in-plane lattice-matched to GaN. So far, state-of-the-art optoelectronic devices using lattice matched InAlN/GaN heterostructures have been grown by metal organic vapour phase epitaxy exclusively. There have been a few reports of molecular beam epitaxy growth of InAlN/GaN heterostructures, though their well-controlled growth still remains fundamental challenge. This work summarizes the state of the art of high reflectivity nitride DBRs, reports on the MBE growths and characterization of both lattice-mismatched AlGaN/GaN and lattice-matched InAlN/GaN DBRs with focus on the current status of lattice-matched InAlN/GaN DBRs.

Fecha: viernes, 27 de marzo de 2009
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: "Nanodiamond micromechanical resonators"
Ponente: Eugenio Sillero Herrero
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación,Universidad Politécnica
Resumen:
Los nuevos sistemas de telecomunicaciones presentan cada vez frecuencias de operación más elevadas y estrategias de multiplexación en frecuencia más agresivas. Por ello, el desarrollo de filtros de alta frecuencia con factores de calidad elevados es una necesidad creciente en el mercado de las telecomunicaciones. En este seminario se presentará una tecnología para la fabricación de resonadores micromecánicos que pueden satisfacer dicha necesidad. Se comenzará repasando el principio de funcionamiento de estos resonadores y revisando el estado del arte. Seguidamente se presentará la tecnología de fabricación para el desarrollo de microresonadores basados en diamante nanocristalino. Este material ofrece una serie de ventajas para la fabricación de resonadores debido a su rigidez ((E/r)1/2 = 17800 m/s), robustez y posibilidades de integración con otros materiales. Se discutirá la caracterización de diversas estructuras resonantes y se presentarán sus propiedades. A partir de la caracterización de los dispositivos fabricados se extraerán los parámetros materiales del diamante nanocristalino.

Fecha: viernes, 13 de marzo de 2009
Hora: 12:00 hora
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: "Slot-Waveguides for biochemical sensing and other optofluidic applications"
Ponente: Carlos Angulo Barrios
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación, Universidad Politécnica
Resumen:
The slot-waveguide has received considerable attention since its invention at Cornell University in 2003. This guided-wave structure consists of two strips of high refractive-index materials separated by a subwavelength-scale low refractive-index region. The fundamental guided-mode exhibits high electric-field amplitude, and optical intensity in the low-index region at levels that cannot be achieved with conventional waveguides. This remarkable characteristic makes possible to greatly increase light-matter interaction at the nanoscale, leading to applications ranging from highly efficient all-optical switching to ultrahigh-sensitivity optical sensors. In this talk, I will present the first experimental demonstration of a slot-waveguide operating as a biochemical sensor (homogeneous and biomolecule sensing). In addition, I will show the capability of slot-waveguides to trap liquids inside their nanometer-sized slot region, which can be used for optofluidic applications such as liquid-based permanent and rewritable integrated photonics, process monitoring, optofluidic memories and analysis of liquid-solid interfacial forces at the nanoscale.

Fecha: viernes, 6 de marzo de 2009
Hora: 12:00
Lugar: C-206.1, Edificio López Araujo, ETSI Telecomunicación. [Cómo llegar]
 
Título: InAs/(Ga,In)(N,As) Quantum Dot LEDs Emitting at 1.3-1.5 µm
Ponente: M. Montes Bajo
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación, Universidad Politécnica
Resumen:
En la actualidad hay un gran interés en las heteroestructuras basadas en puntos cuánticos autoensamblados de InAs para lograr dispositivos emisores de luz basados en GaAs a las longitudes de onda de las ventanas de comunicación por fibra óptica de 1.3 y 1.55 µm. La estrategia más común para lograr alcanzar estas longitudes de onda consiste en variar la composición de las barreras de los puntos cuánticos. Recientemente se ha logrado fotoluminiscencia a temperatura amibente a 1.45 µm con una anchura a media altura de 38.5 meV utilizando puntos de InAs cubiertos con capas de (Ga,In)(N,As) con el 15% de In y el 1.2% de N. El objetivo de este trabajo es demostrar el funcionamiento de estas estructuras en dispositivos reales. Se mostrarán las característiscas de electroluminiscencia (EL) de una serie de LED de puntos cuánticos de InAs/(Ga,In)(N,As) con contenidos de In entre el 0 y el 15% y contenidos de N entre el 0 y el 2%. Con estos LED se consigue emisión a temperatura ambiente en todo el rango entre 1.3 y 1.5 µm. Se identificará el origen de los diferentes picos presentes en los espectros de EL y se analizará el impacto que tienen sobre la eficiencia de los LED la incorporación de N y los tratamientos térmicos posteriores al crecimiento de los dispositivos. Asimismo se mostrarán algunos resultados utilizando otro tipo de estructuras, como puntos de InAs/GaAsSb.

Fecha: viernes, 27 de febrero de 2009
Hora: 12:00
Lugar: C-206.1, Edificio López Araujo, ETSI Telecomunicación. [Cómo llegar]
 
Título: Fabricación, diseño y caracterizaci&oacunte;n de filtros de ondas acústicas de superficie
Ponente: G. Fuentes Iriarte
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación, Universidad Politécnica
Resumen:
Los dispositivos de ondas acústicas superficiales (SAW, surface acoustic waves) son utilizados habitualmente en una gran variedad de equipos de electrónica de consumo como por ejemplo los aparatos de televisión, los video reproductores, los teléfonos móviles etc. En general, allí donde sea necesario filtrar una frecuencia de transmisión o recepción (es decir, en todos los sistemas que requieran de transmisión inalámbrica de señales) es muy probable que encontremos filtros SAW, encargados de llevar a cabo la tarea de dejar pasar una frecuencia y rechazar otras que puedan estar llegando a la antena al mismo tiempo. Por otra parte, la respuesta de los dispositivos SAW depende del ambiente en que están inmersos, por lo que tienen una demanda cada vez mayor como sensores físicos, químicos y biológicos. El hecho de que puedan transmitir la señal sin cable -efecto antena- permite concebir sensores inalámbricos para ambientes agresivos. En esta propuesta se pretenden desarrollar filtros SAW basados en nitruros III-V (AlN, AlGaN). Estos materiales son semiconductores de gap ancho y directo, con notable velocidad del sonido, que además de ser piezoeléctricos presentan una enorme estabilidad mecánica, térmica y físico-química. Son por tanto candidatos ideales para la realización de sensores para ambientes extremos (alta temperatura, altas dosis de radiación, medios tóxicos, etc.). Además, son serios candidatos para remplazar a los dispositivos utilizados actualmente, que presentan claras desventajas como altos costes de manufacturación así como serias dificultades de integración en la tecnología CMOS (empleada hoy en día en la fabricación del 95% de los circuitos integrados existentes en el mercado) debido a las altas temperaturas que se requieren para el crecimiento de los substratos. Se utilizarán varias técnicas de crecimiento, distintos sustratos y diseños del dispositivo con objeto de mejorar su respuesta en frecuencia. Parte esencial de su caracterización consiste en investigar el comportamiento térmico de estos filtros. Finalmente, se pretende depositar materiales orgánicos (e.g., polímeros) que sean sensibles a ciertos gases (CO, NO, etc.) para fabricar sensores químicos.

Fecha: viernes, 20 de febrero de 2009
Hora: 12:00
Lugar: Sala 206-1. Edificio López Araújo, ETSI Telecomunicación [Cómo llegar]
 
Título: Optimización de un sistema de "sputtering"para el depósito de películas delgadas de nitruro de aluminio
Ponente: Rocío San Román Alonso
Organismo: Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), de la E.T.S.I. Telecomunicación, Universidad Politécnica
Resumen:
Sumamente resistente a elevadas temperaturas, con bajo coeficiente de expansión térmica, buenas propiedades dieléctricas, no tóxico, y compatible con la tecnología estádar basada en silicio, el AlN es un material empleado típicamente en dispositivos electrónicos y sobre el cual existe un creciente interés por los estudios que lo relacionan con dispositivos que mueven grandes sumas de dinero al año (filtros de ondas acústicas, resonadores). El crecimiento de AlN por sputtering se ha extendido enormemente en los últimos diez años, desplazando a las técnicas tradicionales como son la deposición química CVD -Chemical Vapor Deposition- o la epitaxia por haces moleculares MBE - Molecular Beam Epitaxy - El motivo del auge de esta ténica hay que buscarlo en alguna de sus características principales, pudiendo destacar la posibilidad de realizar depósitos a temperatura cercana a la ambiente, la libertad en la elección del tamaño, forma y características del sustrato o su económica puesta en marcha y mantenimiento. Por todo lo brevemente mencionado se ha montado un sistema de pulverización catódica especialmente diseñado para el crecimiento de aluminio y de nitruro de aluminio por sputtering reactivo, optimizando su estructura y los diversos parámetros de crecimiento con objeto de obtener láminas de AlN con las características adecuadas para cada aplicación desde el AlN amorfo como capa aislante en MEMS, hasta el AlN de calidad cristalina elevada para aplicaciones piezoelétricas.

Fecha: viernes, 18 de julio de 2008
Hora: 12:00
Lugar: Sala C-206-1. Edificio López Araujo (C), E.T.S.I. Telecomunicación (UPM) [Cómo llegar]
 
Título: Research activities of Oxide semiconductors at the Research Institute of Electronics
Ponente: Atsushi Nakamura
Organismo: Research Institute of Electronics (RIE), Shizuoka University, 3-5-1 Johoku, Hamamatsu, Shizuoka, Japan
Resumen:
RIE is a university research institute conducting research in a variety of semiconductor and optelectronic materials and devices as display devices. RIE is an institute for Television research to innovate opto-, electronics based on nanotechnology. We are developing new nanostructure formation techniques based on self-organized crystal growth and novel, semiconductor quantum photonic devices for establishing nanovision science and related technologies. Nanostructures are expected for the application of next-generation high-performance devices in utilizing large quantum effects. But it is very difficult to build high quality nanostructures by using conventional micro-fabrication methods. We are trying to make confined nanostructures by utilizing self-organization phenomenon in semiconductor epitaxial growth. Oxide semiconductors such as ZnO and its related alloys are investigated in Photonic device laboratory. Layer growth is made by plasma-assisted MOCVD. Light emitting diodes in the range of visible light are being investigated on the ZnO based materials. Photodetectors from visible to UV range are also being investigated with a support from ISOM. Nanocolums and nanowires are grown toward new concept sensors are studied. These activities involving Photonic device laboratory (Temmyo-lab.) will be briefly described.

Fecha: jueves, 17 de julio de 2008
Hora: 12:00
Lugar: Sala C-206-1. Edificio López Araujo (C), E.T.S.I. Telecomunicación (UPM) [Cómo llegar]
 
Título: Deep Level Optical Spectroscopy: Approach to Investigate Defects in GaN-AlGaN Materials and Devices
Ponente: Steven A. Ringel.
Organismo: Professor and Neal A. Smith Chair in Electrical Engineering Director, Ohio State University Institute for Materials Research
Resumen:
The great interest in GaN, AlGaN, InGaN and related heterostructures for both RF power electronics and a variety of optoelectronics is due to the wide bandgaps that can be accessed in these materials coupled with the fact that device heterostructures with controlled doping can be created with reasonable material quality. As a result, III-Nitrides are revolutionizing the field of solid state lighting that is critical to our energy usage situation and are also resulting in unprecedented transistor performance. However, these applications greatly stress the constituent materials during operation and there is extreme interest to understand the nature of device degradation as it relates to the material defects present in these structures. Moreover, the nitride materials are fascinating from a defect physics perspective due to the fact that they incorporate much higher defect densities than do all other successful III-V technologies and their large bandgap energies make quantitative electronic characterization of these defects extremely challenging. This presentation will provide an overview of the development and application of Deep Level Optical Spectroscopy (DLOS) and a wide range of variations of DLOS that are currently being used to explore traps in GaN, AlGaN/GaN FETs and in bulk AlGaN materials of interest for ultraviolet and blue emitting applications.

Fecha: miércoles, 2 de julio de 2008
Hora: 12:00
Lugar: Sala 206-1. Edificio López Araújo, ETSI Telecomunicación [Cómo llegar]
 
Título: Metamorphic III-V Materials for Infrared and High Speed Devices Based on Sub-Lattice Specific Grading
Ponente: Steven A. Ringel.
Organismo: Professor and Neal A. Smith Chair in Electrical Engineering Director, Ohio State University Institute for Materials Research
Resumen:
III-V compounds with lattice constants between InP and InAs provide access to a variety of important future device technologies including near-teraherz electronics based on the extremely high electron mobility of InAs to direct energy conversion of infrared photons in a thermophotovoltaic format. The ability to create the necessary heterostructures with very low defect concentrations so that such devices may be feasible requires a high quality, lattice matched substrate on which they can be grown. This presentation will focus on the novel use of the group V (anion) sub-lattice as a preferred sublattice with which to achieve metamorphic grading in MBE growth as compared with the more usual group III (cation) sublattice. Comparisons between both will be described from the viewpoint of dislocation and phase segregation issues and a true virtual InAs substrate (grown on InAsP/InP) is described with record high mobilities for strain relaxed InAs material.

Fecha: martes, 1 de julio de 2008
Hora: 12:00
Lugar: Sala 206-1. Edificio López Araújo, ETSI Telecomunicación [Cómo llegar]
 
Título: Epitaxial Integration of III-V Semiconductors, Devices and Solar Cells with Si via Lattice Engineering
Ponente: Steven A. Ringel.
Organismo: Professor and Neal A. Smith Chair in Electrical Engineering Director, Ohio State University Institute for Materials Research
Resumen:
The ability to capitalize on Si wafer technology as both an active and passive platform for III-V devices has been in great demand for technologies ranging from III-V enhanced channels in Si electronics and optoelectronic integrated circuits on Si, to high performance solar cells with lower cost. This presentation covers recent work based on two all-epitaxial pathways that open avenues for transferring a variety of III-V hetrostructures onto Si platforms: lattice-graded GaAsP on GaP/Si and lattice-graded SiGe. Both approaches provide metamorphic templates that support integration of AlGaInAsP-based materials that for the first time can be integrated with low defect densities onto Si in a scaleable process. The talk will focus on MBE growth of III-V materials and devices on Si, including laser diodes and LEDs, but will emphasize solar cells as the issue of clean and renewable energy has massively re-invigorated this field. An emphasis is also give to the fundamentals and importance of interface control in heterovalent MBE growth and the issue of defect control and impact on materials and devices.

Fecha: lunes, 30 de junio de 2008
Hora: 12:00
Lugar: Sala 206-1. Edificio López Araújo, ETSI Telecomunicación [Cómo llegar]
 
Título: El Hogar Digital
Ponente: Juan José González Menaya
Organismo: Telefónica I+D. Madrid
Resumen:
Para los próximos años se espera una gran revolución en el hogar digital. Existen numerosos estándares internacionales y proyectos europeos trabajando para desarrollar la tecnología que permita desplegar los nuevos servicios que demanda un entorno de hogar digitalizado.
Al trabajar en la división de "Servicios y comunicaciones para el hogar digital" de Telefónica I+D, haré una introducción sobre las líneas actuales de investigación en las que estamos involucrados. Para terminar, explicaré los trabajos hasta ahora realizados en el proyecto europeo INTERMEDIA, dentro del sexto programa marco de UE, en el que participamos.

Fecha: viernes, 20 de junio de 2008
Hora: 12:00
Lugar: Sala 206-1. Edificio López Araújo, ETSI Telecomunicación [Cómo llegar]
 
Título: Magnetic resonance imaging of the lungs with the use of hyperpolarised gases
Ponente: Angelos Kyriazis
Organismo: PhD researcher of the PHELINET group Instituto de Estudios Biofuncionales, Universidad Complutense de Madrid
Resumen:
Magnetic resonance imaging (MRI) is a standard non-invasive clinical technique for the imaging of the interior of the human body. It is based on the measurement of the response of hydrogen nuclei (protons) to radiofrequency pulses. Protons are abundant in the human body due to the presence of water in every living tissue. This way, almost every area of the body can be imaged satisfactorily.
An exception are the lungs, where the density matter is very low which means that they are almost devoid of water. A proposed solution (which is the topic of this discussion) is the use of appropriate inhalable contrast agents, such as helium and xenon.
These noble gases possess no magnetic momentum, which implies that they are not viewable with MRI. Therefore, before use these gases are polarised by force. Their artificial polarisation not only gives a very strong signal of the lungs, but also makes it possible to quantify the health state of the lung-tissue.
Polarised noble gas lung imaging is a promising method under research and constant development for the last 10 years.

Fecha: viernes, 13 de junio de 2008
Hora: 12:00
Lugar: Sala 206-1. Edificio López Araújo, ETSI Telecomunicación [Cómo llegar]
 
Título: Cálculos de Alto Rendimiento con Tarjetas Gráficas
Ponente: Mario J. Martin
Organismo: Instituto Nacional de Tecnología Aeroespacial Esteban Terradas (INTA)
Resumen:
Desde hace escasamente cuatro o cinco años las tarjetas gráficas han despertado el interés para su uso en aplicaciones de cálculo numérico. De esta forma ha aparecido el concepto GPGPU "General Purpose Graphics Processor Units" que viene a definir la utilización de tarjetas gráficas para aplicaciones de propósito general.
El uso de las tarjetas gráficas para computación científica general se ha visto motivado por el espectacular crecimiento de las tarjetas gráficas en cuanto a rendimiento en cálculo de coma flotante que actualmente superan al de un procesador convencional en varios órdenes de magnitud. Gracias a esta evidente potencia de cálculo, las tarjetas gráficas han trascendido su función original dedicada a la aceleración de gráficos en aplicaciones de visualización, para convertirse en una herramienta de cálculo para aplicaciones científicas; desde cálculos con matrices [1], operadores de algebra lineal [2] o cálculo numérico de la dinámica de fluidos (CFD) [3] [4] En la presentación se pretende hacer una introducción al fascinante mundo de las tarjetas gráficas y una de sus posibles aplicaciones mostrando el trabajo que se está realizando en el INTA en colaboración con IMDEA que consiste en comprobar la viabilidad del desarrollo de un código CFD para resolver las ecuaciones de Euler y Navier-Stokes para aplicaciones industriales; concretamente para el diseño aerodinámico.
1. Bolz J., Farmer I., Grinspun E., Schröder P., /Sparce matrix solvers on the GPU: Conjugate gradients and multigrid/, ACM Transactions on Graphics 22, 3, 917-924, (2003).
2. Krüger J., Westermann R., Linear algebra operators for GPU implementation of numerical algorithms, ACM Transactions on Graphics 22-3, (2003).
3. Trond Runar Hagen, Knut-Andreas Lie, and Jostein r. Natvig, Solving the Euler equations on graphics processing units/, Lecture Notes in Computer Science, Vol 3994, 220-227, (2006).
4. Harris M., /Fast fluid dynamics simulation on the GPU/, GPU Gems, Addison Wesley, 637-665, (2004).
5. Tobias Brandvik and Grahan Pullan, /Acceleration of a 3D Euler solver using commodity graphics hardware/, 46th AIAA Aerospace Sciences Meeting and Exhibit, AIAA 2008-607, (2008).

Fecha: viernes, 6 de junio de 2008
Hora: 12:00
Lugar: Sala 206-1. Edificio López Araújo, ETSI Telecomunicación [Cómo llegar]
 
Título: Sólidos amorfos ideales: sistemas modelo de la materia desordenada
Ponente: Prof. Manuel Laso
Organismo: Departamento de Ingeniería Química, ISOM, ETSII, UPM
Resumen:
El primer tipo de sólido amorfo ideal, el empaquetamiento aleatorio denso de esferas duras, o Tipo I, fue identificado a finales de los 50 (Bernal & Mason, Nature 188, 910-911 (1960)). La determinación del segundo tipo, el empaquetamiento aleatorio denso de cadenas de esferas duras, o Tipo II, y de sus características es mucho mas reciente (Karayiannis & Laso, Phys. Rev. Lett. 100, 050602 (2008)).
En este seminario se describe brevemente el descubrimiento, la estructura y las aplicaciones del sólido amorfo Tipo II. También se describe la identidad observada (e inesperada) de las leyes topológicas universales de escala de "nudos" y de "entralazamientos" entre las cadenas del sólido amorfo ideal II (Laso & et al. Nature Physics, submitted 2008). Esta identidad tiene repercusiones en áreas tan diferentes como geometría combinatoria, física de polímeros, materia condensada y biofísica.

Fecha: viernes, 30 de mayo de 2008
Hora: 12:00
Lugar: Sala 206-1. Edificio López Araújo, ETSI Telecomunicación [Cómo llegar]
 
Título: Crecimiento ordenado de Nanocolumnas de GaN sobre Si mediante Epitaxia de Haces Moleculares
Ponente: María Utrera
Organismo: ISOM-Depto Ing Electrónica
Resumen:
Durante las últimas décadas, Nanocolumnas hexagonales del grupo III han sido crecidas sobre Si(111) [1,2] y mas recientemente sobre Si(100) [3] mediante Epitaxia de Haces Moleculares (MBE).
Las Nanocolumnas autoensambladas son crecidas a lo largo del eje c (c-axis) de la estructura hexagonal manteniendo su propio parámetro de red, diferente al del sustrato. Estas Nanoestructuras presentan gran calidad cristalina de acuerdo con medidas de Microscopía de transmisión de electrones (TEM) y una altísima eficiencia óptica (la intensidad de la fotoluminiscencia es de varios ordenes de magnitud superior a la de capas compactas de GaN ). La relajación de las Nanocolumnas se produce en la intercara con el sustrato y a través de su superficie, por lo que su volumen queda libre de defectos extensos y relajado ( strain-free).
Sin embargo, las Nanocolumnas autoemsambladas sufren dispersión en diámetros, altura y distribución en el plano , lo cual provoca dificultades en el procesado de las heteroestructuras nanocolumnares para la obtención de dispositivos reales.
El trabajo que aquí se presenta, va dirigido a la obtención de matrices de Nanocolumnas ordenadas y localizadas de GaN mediante la utilización de distintos tipos de máscaras de nanoagujeros ( Ti, SiO2) sobre el sustrato de crecimiento, Si(100) o Si(111). El objetivo básico ha consistido en conseguir que las Nanocolumnas crezcan de acuerdo con el patrón definido en la máscara. Es de esperar que la consecución de este reto haga posible el desarrollo de matrices de Nanoemisores en el Rango ultravioleta.

Fecha: viernes, 23 de mayo de 2008
Hora: 12:00
Lugar: Sala 206-1. Edificio López Araújo, ETSI Telecomunicación [Cómo llegar]
 
Título: A comparative study by ion beam analysis and X-ray diffraction in GaN-based HEMT heterostructures
Ponente: Fernando González-Posada Flores
Organismo: Proyecto: KORRIGAN (Key Organisation for Research on Integrated Circuits in GaN Technology)
Resumen:
AlGaN/GaN heterostructures (HS) are key structures to fabricate GaN-based quantum building blocks and to perform band gap engineering. In fact the use of one or multiple HS of the (Al,Ga,In)N system has led to present visible and UV light emitting diodes and laser diodes, to Bragg reflectors, super-lattices, high electron mobility transistors (HEMT), UV photodetectors, resonant tunnelling diodes, etc. The Al content in AlxGa1 ? xN/GaN heterostructures has been determined by X-ray diffraction (XRD) and contrasted with absolute measurements from ion beam analysis (IBA) methods. For this purpose, samples with 0.1< x < 0.3 grown by metal organic chemical vapour deposition on sapphire substrates have been studied. XRD and IBA corroborate the good epitaxial growth of the AlGaN layer, which slightly deteriorates with the incorporation of Al for x > 0.2. The assessment of Al incorporation by XRD is quite reliable regarding the average value along the sample thickness. However, XRD analysis tends to overestimate the Al fraction at low contents, which is attributed to the presence of strain within the layer. For the highest Al incorporation, IBA detects a certain Al in-depth compositional profile that should be considered for better XRD data analysis.

Fecha: viernes, 9 de mayo de 2008
Hora: 12:00
Lugar: Sala 206-1. Edificio López Araújo, ETSI Telecomunicación [Cómo llegar]
 
Título: Growth, doping and characterization of polar / non-polar, InN/InGaN and those nano-structures
Ponente: Yasushi NANISHI
Organismo: Department of Photonics, School of Science and Engineering, Ritsumeikan University, 1-1-1 Noji-Higashi, Kusatsu-shi,Shiga 525-8577 , Japan.
Resumen:
Six years have passed since narrow band gap of InN was first reported. Now, narrow band gap of around 0.65 eV have widely recognized after several years of discussion among relevant scientists. This new finding expanded application field of group III nitrides and those alloy system from 6.2 eV of AlN to 0.65 eV of InN. This attracted considerable attentions to InN and related alloys. However, many scientific and technical issues hinder those applications to devices. These include, very high concentration of residual donors, surface accumulation layer, high density dislocations due to large lattice mismatch to substrate, GaN and AlN, p-type doping and formation of high quality hetero-interface.
In this presentation, 1) attempts to decrease dislocations, 2) effect of dislocation on optical properties of InN, 3) non-polar growth of InN attempting to suppress surface accumulation of carriers, 4) Mg doping to both polar and non-polar InN, 5) Mg doping to InGaN and 6) characterization of Mg-doped InN by EXAFS and positron annihilation spectroscopy will be shown.
As attempts to decrease dislocations, (1) re-growth on micro-faceted InN template and (2) growth of position-controlled InN nano-columns will be shown. TEM study on nanocolumns demonstrated remarkable effect of this technology to reduce or eliminate threading dislocations in InN.
Effect of dislocations on optical properties of InN was carried out by CL measurements. We found that highly dislocated area corresponds to non-radiative area in CL measurements.
A-plane InN on R-plane sapphire and M-plane InN on LiAlO2 have been successfully grown by RF-MBE. Bulk carriers and surface carriers were estimated by sheet carrier dependence on film thickness. Unfortunately, formation of surface accumulation layer, however, could not be removed by these non-polar growths. Non-polar growth with atomically flat surface should be needed, at least, to suppress formation of accumulation layers.
Mg is doped not only to N-polar C-plane InN but also to A-plane and M-plane InN films. InGaN alloys are also doped by Mg. All the samples including InGaN showed Mott-Schottky curves which imply formation of p-type layers under surface accumulation layers. However, p-type conductivity has not been confirmed by Thermopower method. Mg doping limits to keep single crystal InN, minimum Mg-doping level to observe p-type conversion were both compared among C-plane, A-plane and M-plane InN films.
EXAFS measurement revealed that Mg sits substitutionally on In sublattice acting as an acceptor impurity. Positron annihilation spectroscopy implied that small amount of Mg doping decreases VIn related point defects. Higher concentration of Mg doping, however, increases VIn related point defects. This corresponds to re-increase of electrons after excess Mg doping to InN.

Fecha: martes, 15 de abril de 2008
Hora: 12:00
Lugar: Sala 206-1. Edificio López Araújo, ETSI Telecomunicación [Cómo llegar]
 
Título: Research and Development of AlGaN/GaN High Power and High Frequency Electronic Devices under Support of Japanese Government
Ponente: Yasushi NANISHI
Organismo: Department of Photonics, School of Science and Engineering, Ritsumeikan University, 1-1-1 Noji-Higashi, Kusatsu-shi,Shiga 525-8577 , Japan.
Resumen:
With its high mobility and high saturation velocity, high breakdown electric field and good thermal conductivity, AlGaN/GaN heterostructure system attracted much attention as a promising material system for application to high power and high frequency transistors. In contrast with these high potential, actual performance of these devices ten years ago was far below the level of those we expected. We formed NEDO's regional consortium and started nitride electronic device project in 1999 for 3 years. Japanese government then recognized the importance of this research proposal considering rapidly increasing demands for next generation wireless communication, and started to support development of GaN high power and high frequency electronic devices as 5 year National project.
In this seminar, I would like to present firstly on overview of NEDO's National project, secondly on development of device technologies and state of the art performances of these devices. Finally, investigation on correlation between epi-wafer quality and device performances will be presented.
In the overview of NEDO's project, main concept, structure, targets and budget of this project will be introduced. As for device technologies and device performances, newly developed technologies such as field plate, recessed gate, digital pre-distortion circuit and dual field plate will be presented. Remarkable effects on device performances will also be presented. As examples of these performances, 230 W single chip operation at 2 GHz, record high output power of 416 W from a single packaged amplifier and 758 W pulsed operation of a single packaged device both at 2 GHz will be presented. Successful operation of dual field plate device which enabled simultaneous improvement of linear gain and output power will also be presented. Device performances at 5 GHz and 26 GHz will also be shown.
As for correlation between epi-wafer quality and device performances, (1) effect of crystal defects in the substrates, (2) correlation between crystal defect in i-GaN and buffer leakage, (3) origin of gate leakage current, (4) effect of surface traps, (5) electric field monitoring method by KFM, (6) effect of AlN molar fraction, thickness and morphology of AlGaN layer and (7) temperature distribution measurement method of operating devices by micro-Raman scattering method will be presented. Here it will be shown that buffer leakage mechanism will be explained successfully by space-charge-limited current and breakdown can be explained by traps-filled-limit voltage. As a result, on the contrary of our common sense, epi-structure with thinner i-GaN layer and with higher threading dislocations sometimes help to suppress buffer leakage current and to obtain higher source-drain breakdown voltage, as threading dislocations in i-GaN work as trapping centers of carriers. Clear correlation between gate leakage current and screw dislocation in AlGaN will also be shown.

Fecha: lunes, 14 de abril de 2008
Hora: 12:00
Lugar: Sala 206-1. Edificio López Araújo, ETSI Telecomunicación [Cómo llegar]
 
Título: c-plane, a-plane, m-plane GaN quantum dots, quantum wires and quantum wells: how to play with the growth mode?
Ponente: Prof. Bruno Daudin
Organismo: CEA/Grenoble, Department of Fundamental Research on Condensed Matter
Resumen:
Quantum dots (QDs) are of particular interest in highly defective nitride materials and are possible candidates to form active layers of a new generation of light emitting diodes. In particular, growth of nonpolar QDs is especially attractive to face the issue of internal electric field present in [0001] heterostructures, detrimental to radiative recombination efficiency. Along these lines molecular beam epitaxy growth of polar and non polar GaN QDs will be described. Their structural properties will be discussed. In particular, it will be shown that a wide variety of morphological shapes, ranging from quantum wells to QDs and quantum wires, can be obtained depending on growth conditions. The optical properties of non polar [11-20] and [1-100] dots will be presented and compared to that of their polar [0001] counterparts. As expected, it is found that luminescence decay time is shorter (around 200 ps) in non polar QDs than in polar ones (in the 10 ns - 100 ?s range), due to electric field reduction.

Fecha: miércoles, 7 de noviembre de 2007
Hora: 12:00
Lugar: C-206.1 ETSI Telecomunicación [Cómo llegar]
 
Título: Fundamental aspects of solid state lighting V
Ponente: Klaus Ploog
Organismo: Paul Drude Institut. Berlin
Resumen:

Fecha: viernes, 7 de septiembre de 2007
Hora: 12:00
Lugar: C-206.1 ETSI Telecomunicación [Cómo llegar]
 
Título: Fundamental aspects of solid state lighting IV
Ponente: Klaus Ploog
Organismo: Paul Drude Institut. Berlin
Resumen:

Fecha: jueves, 6 de septiembre de 2007
Hora: 12:00
Lugar: C-206.1 ETSI Telecomunicación [Cómo llegar]
 
Título: Fundamental aspects of solid state lighting III
Ponente: Klaus Ploog
Organismo: Paul Drude Institut. Berlin
Resumen:

Fecha: jueves, 5 de julio de 2007
Hora: 12:00
Lugar: C-206.1 ETSI Telecomunicación [Cómo llegar]
 
Título: Fundamental aspects of solid state lighting II
Ponente: Klaus Ploog
Organismo: Paul Drude Institut. Berlin
Resumen:

Fecha: miércoles, 4 de julio de 2007
Hora: 12:00
Lugar: C-206.1 ETSI Telecomunicación [Cómo llegar]
 
Título: Group III-Nitrides - from bioelectronics to nanotechnology
Ponente: M. Eickhoff
Organismo: Walter Schottky Institut, de la Technische Universitat de Munich.
Resumen:
lGaN/GaN electrolyte gate field effect transistors bear a great potential as sensor devices for electronic detection of biochemical processes. In addition, their high pH-sensitivity allows the electronic detection of enzymatic biocatalytical reactions accompanied by local pH changes.
For the realization of reliable and reproducible biosensor devices, the preparation of a well defined interface between semiconductor device and molecules acting as bioreceptors is an important requirement. Therefore, we have analyzed the influence of the immobilization process on the characteristics of enzymes immobilized on GaN surfaces. For this purpose we have prepared enzyme-modified field effect transistors (EnFETs) by physisorption of penicillinase multilayers as well as by covalent immobilization of penicillinase monolayers using Schiff-Base formation. The response characteristics of both kinds of EnFETs to penicillin is compared. Both the calibration curve and the stability of the devices are shown to be strongly affected by the applied immobilization technique. It is demonstrated that covalent immobilization results in the formation of an enzyme (sub-) monolayer and allows the preparation of EnFETs with highly reproducible sensing characteristics.
The application of semiconductor nanostructures in chemical or biochemical sensors can lead to an improved sensitivity or can even gain new functionalities. Employment of nanowires as electrical transducers is expected to improve the signal to noise ratio for electrical detection of changes in the surface potential. GaN quantum dots, which show efficient luminescence also at room temperature, can be used as nano-optical transducers for chemically induced changes of the surface potential and would allow the realization of spatially-resolved optical sensing.
The properties of GaN quantum dots in an AlN matrix for such applications and the basic sensing mechanisms as well as first results of gas sensing devices are discussed.

Fecha: miércoles, 4 de julio de 2007
Hora: 16:00
Lugar: C-200 ETSI Telecomunicación [Cómo llegar]
 
Título: Fundamental aspects of solid state lighting I
Ponente: Klaus Ploog
Organismo: Paul Drude Institut,
Resumen:

Fecha: martes, 3 de julio de 2007
Hora: 12:00
Lugar: C-206.1 ETSI Telecomunicación [Cómo llegar]
 
Título: Giant magneto-impedance effect in electrodeposited CoP layers and CoP-Cu-CoP sandwich structures
Ponente: Miguel González-Guerrero
Organismo: ISOM-UPM
Resumen:
The giant magneto-impedance (GMI) effect is the large change of impedance that a magnetic structure exhibits under the application of an external magnetic field at frequencies commonly in the order of MHz [1]. Both the real and the imaginary parts of the impedance of a ferromagnetic material through which an ac current I = I0exp(-jwt) circulates depend of its magnetic permeability. The resistance changes are due to the skin effect [2], according to which the current density experiments a decay of 1/e of its value in the surface at a distance of inside the ferromagnetic conductor, called the penetration depth. The reactive changes are due to the linear dependence between the internal self indutance of the magnetic film and the magnetic permeability. The GMI effect has been studied in amorphous ferromagnetic electrodeposited CoP layers and CoP-Cu-CoP sandwich structures as a function of the thickness of the ferromagnetic and the conductive films, the frequency of the driving current and the magnetic anisotropy of the ferromagnetic material. Values of over 100% for single ferromagnetic layers and over 1000 % for sandwich structures have been obtained. The results are interpreted in terms of two simple theoretical models (one for homogeneus ferromagnetic fims and the other for ferromagnetic-conductive-ferromagnetic structures) based on the classical one, showing a good agreement with the measured results and letting us to give an estimation of the magnetic permeability values and its evolution with the frequency. The physical background of the effect is demonstrated and the influence of the external self inductance (geometry) of the samples is highlighted [3]. Finally, some feasible applications [4] of the GMI efect in magnetic sensors and devices will be summarized.
[1] Panina, L.V.; Mohri, K.; Uchiyama, T., Physica A, 241, 429 (1997)
[2] L.D. Landau and E.M. Lisfshitz, Electrodynamics of Continuous Media. In: , Pergamon, Oxford (1975), p. 195
[3] Kurlyandkaya, G., Barandiaran, J.M.; Garcia-Arribas, A. and Munoz, J.L.; IEEE Trans. Magn., 38, 3051 (2002)
[4] Tannous, C. and Gieraltowsky, J.; J. Mater. Sc.: Mater. in Electronics, 15, 125 (2004)

Fecha: viernes, 29 de junio de 2007
Hora: 12:00
Lugar: C-206.1 ETSI Telecomunicación [Cómo llegar]
 
Título: E-beam nano-lithography: Present and future at Institute for Systems based on Optoelectronics and Microtechnology
Ponente: David López-Romero
Organismo: ISOM-UPM
Resumen:
ISOM purchased recently an e-beam lithography tool with 10 nm line resolution. ISOM is now able to reduce the fabrication scale to nanometers. During this talk we will discuss in detail the features of the system and the issues related to the techniques for nanodevice pattern-transfer.

Fecha: viernes, 22 de junio de 2007
Hora: 12:00
Lugar: C-206.1 ETSI Telecomunicación [Cómo llegar]
 
Título: "Capping of InAs quantum dots studied at the atomic scale by cross-sectional scanning tunneling microscopy"
Ponente: Jose Maria Ulloa
Organismo: Department of Applied Physics, Eindhoven University of Technology, The Netherlands
Resumen:
The efforts to extend the emission wavelength of InAs quantum dots (QD) to the 1.3-1.55 μm region have lead to different approaches in which different capping materials and procedures are employed. To understand and control the capping process is of crucial importance because critical issues like dot decomposition, intermixing, As/P exchange and phase separation in the capping layer depend on the capping material and growth procedure. We have used cross-sectional scanning tunneling microscopy to analyze at the atomic scale how the above mentioned effects influence the structural properties of InAs QDs grown by MBE on GaAs and InP substrates. We show that critical QD properties like the height (which determines the quantum confinement) can be controlled by an adequate selection of the capping method.

Fecha: viernes, 15 de junio de 2007
Hora: 12:00
Lugar: C-206.1 ETSI Telecomunicación [Cómo llegar]
 
Título: III-nitride microcavity light emitting diodes and lasers
Ponente: M. Ilegems
Organismo: Institute of Quantum Electronics and Photonics, Ecole Polytechnique Fédérale de Lausanne
Resumen:
This talk will give an overview of the activities at EPF-Lausanne on nitride-based light emitting diodes and vertical cavity lasers, and on the study of polariton effects observed in the strong exciton-photon coupling regime, including recent results on the possible observation of polariton lasing at room temperature. Marc Ilegems received his degrees in engineering physics from the University of Brussels and a doctorate in electrical engineering from Stanford University. He presently is emeritus professor at EPF Lausanne, where he served as director of the Semiconductor Device Physics Laboratory, head of the Physics Department, and director of the Swiss National Program on Quantum Photonics.

Fecha: viernes, 8 de junio de 2007
Hora: 12:00
Lugar: C-206.1 ETSI Telecomunicación [Cómo llegar]
 
Título: Modulation of photonic structures by surface acoustic phonons
Ponente: Mauricio M. de Lima, Jr.
Organismo: Instituto de Ciencia de Materiales, Universidad de Valencia
Resumen:
The study of acoustic excitation of semiconductor-based photonic structures is an emerging field with great potential for new types of photonic manipulation.[1] In this talk, I will report on experiments recently performed on the coherent modulation of semiconductor microcavities as well as of Mach-Zehnder interferometers by electrically stimulated surface acoustic waves. In the case of a bare microcavity, the strong interaction between the high population of non-thermal acoustic phonons and the photons trapped in the cavity gives rise to a tuneable optical superlattice with a folded dispersion and well-defined energy-gaps.[2] Placing a quantum-well with excitonic energy matched to the cavity mode allows the investigation of the acoustic modulation of microcavity-polaritons in the strong-coupling regime.[3] As the phonon population increases, one identifies the transition from a polariton superlattice to an array of weakly coupled polariton wires. Finally, the modulation of Mach-Zehnder interferometers by a collimated beam of surface acoustic phonons leads to ultra-compact and efficient light modulators.[4]
[1] M. M. de Lima, Jr. and P. V. Santos, Reports on Progress in Physics 68, 1639-1702 (2005).
[2] M. M. de Lima, Jr., R. Hey, P. V. Santos, and A. Cantarero, Physical Review Letters 94 (12), 126805 (2005).
[3] M. M. de Lima, Jr., M. van der Poel, P. V. Santos, and J. M. Hvam, Physical Review Letters 97, 045501 (2006).
[4] M. M. de Lima, Jr., M. Beck, R. Hey, and P. V. Santos, Applied Physics Letters 89, 121104 (2006).

Fecha: viernes, 1 de junio de 2007
Hora: 12:00
Lugar: C-206.1 ETSI Telecomunicación [Cómo llegar]
 
Título: "Improved growth mode diagram for plasma-assisted MBE growth of (0001) GaN"
Ponente: Sergio Fernández Garrido
Organismo: ISOM-UPM
Resumen:
The issue of controlling and optimizing GaN epitaxy has become one of the greatest concerns, in order to improve the surface morphology and material quality of current GaN-based devices produced by MBE. In this context, it is particularly important to understand the atomic-scale growth kinetics and their influence on the crystal growth mode. In plasma-assisted MBE growth of (0001) GaN, a common way to control the growth mode and surface structure is by changing the Ga/N flux ratio and/or temperature [1]. With the use of reflection high energy-electron diffraction (RHEED), monitoring of the monolayer-scale growth kinetics have allowed early statements about growth conditions giving either layer-by-layer or or step-flow growth [2,3]. In the meantime, the existence of a metallic Ga surface adlayer was found responsible to govern the adatom surface diffusion [4], surface roughness and surface defect structure [5] of (0001) GaN films. Currently, no direct experimental evidence has been presented that addresses the crucial link between Ga adlayer coverage and crystal growth mode (three-dimensional (3D), layer-by-layer, , step-flow growth). To resolve these issues, we have studied the impact of the Ga adlayer coverage onto the growth mode and island formation mechanism during the homoepitaxial nucleation of (0001) GaN. Determining the Ga adlayer coverage which formed during GaN growth, was facilitated by measuring its postgrowth desorption using quantitative in situ quadrupole mass spectrometry (QMS). Simultaneous observations of the RHEED intensity profile provided measurements of the growth rate and allowed a precise growth mode analysis. Postgrowth atomic force microscopy (AFM) was used to confirm the growth mode and surface structure. Depending on the growth kinetics and Ga adlayer coverage, three distinct RHEED intensity profiles were identified, which could be associated with different growth modes: (a) An increased RHEED intensity contrast with spotty features indicative of 3D island formation under heavy N-rich conditions and low temperatures (ΘGa = 0). (b) Multiple RHEED intensity oscillations with their periods consistent with the growth rate, giving the layer-by-layer r growth of GaN from N-rich to Ga-rich intermediate te growth conditions (0 < ΘGa <1 ML). (c) A slow pseudo-oscillatory RHEED transient indicative of the build-up and desorption of the Ga bilayer (ΘGa > 1 ML) under more Ga-rich growth conditions. GaN films grown under these conditions showed a clear step-flow growth morphology persistent throughout the entire growth. The transition from layer-by-layer to o step-flow growth coincided with the border for the critical Ga adlayer coverage of 1ML, which follows an Arrhenius dependence with growth temperature and an apparent activation energy of 2.2 eV. The second cross-over from layer-by-layer to 3D growth in the N-rich regime gime is also exponentially dependent on growth temperature with a lower activation energy of 1.6 eV. Most striking, the layer-by-layer growth mode of of GaN under N-rich conditions and high temperature seems to provide an alternative approach for achieving smooth 2D GaN films as commonly produced under Ga-rich conditions. [1] B. Heying, R. Averbeck, L. F. Chen, E. Haus, H. Riechert, and J. S. Speck, J. Appl. Phys. 88, 1855 (2000) [2] N. Grandjean and J. Massies, Appl. Phys. Lett. 71, 1816 (1997). [3] B. Daudin and F. Widmann, J. Cryst. Growth 182, 1 (1997). [4] T. K. Zywietz, J. Neugebauer, and M. Scheffler, Appl. Phys. Lett. 73, 487 (1998). [5] G. Koblmüller, J. Brown, R. Averbeck, H. Riechert, P. Pongratz, and J. S. Speck, Jpn. J. Appl. Phys., Part 2 44, L906 (2005).

Fecha: viernes, 18 de mayo de 2007
Hora: 12:00
Lugar: C-206.1 ETSI Telecomunicación [Cómo llegar]
 
Título: "Passivating Layers Influence on the Electrical Characteristics on AlGaN/GaN HEMTs: a Comparative Study"
Ponente: M. Fátima Romero
Organismo: ISOM-UPM
Resumen:
GaN and related compounds are promising semiconductors for high temperature/high power devices [1-3]. Although a significant progress has been already achieved, there are still some areas which need a significant research effort. One of them relates to the origin, understanding and control of the so called current collapse effect in HEMT devices. HEMT output power is highly reduced at microwave frequencies as compared to DC operation [2]. There is significant evidence that the current collapse phenomena is directly related to the surface characteristics of the HEMT structure, and that by proper AlGaN passivation, a reduction in the collapse effects can be achieved [3-4]. However, additional investigation is required to ascertain the nature of the trapped states and the characteristics of GaN based surfaces. This work has focussed on the study of several passivation schemes. In particular, Silicon Nitride (SiN), which is the most extensively layer used. The effect of a N2 plasma pre-treatment prior to PE-CVD SiN deposition was analyzed on AlGaN/GaN HEMT and MIS structures. When N2 plasma is used, a drastic enhancement on HEMT DC output performance was achieved, by increasing the maximum drain current up to 30% respect to no plasma pre-treatment . Besides, hysteresis and knee voltage were highly reduced. In order to investigate drain current dispersion effects, different pulsed measurements were performed revealed a high density of slow interface traps, with a trapping-detrapping time constant from 0.5 seconds up to 0.1 milliseconds, when no N2 plasma pre-treatment is used. In addition, other passivation layers were studied in AlGaN/GaN HEMTs, such as a bilayer (SiO2/SiN) and a high k dielectric material (Ta2O5). A comparative study was carried out through electrical characteristics for both DC and pulsed measurements before and after passivation. [1] U.K.Mishra, P.Parikh, and Y.-F.Wu, Proc. IEEE. 90, 1022, (2002). [2] S.Binari, K.Ikossi, J.Roussos, W.Kruppa, D. Park, H. Dietrich. IEEE Trans Electron Dev. 48, 465 (2001). [3] B.Green, K.Chu, E.Chumbes, J.Smart, J.Shealy, L.Eastman. IEEE Electron Dev. Lett. 21, 268 (2000). [4] R.Ventury, N.Zhang, S.Keller, U.Mishra. IEEE Trans. Electron. Dev. 48, 560 (2001). [5] G.Meneghesso, G.Verzellesi, R.Pierobon, F.Rampazzo, A.Chini, U.Mishra, C.Canali, E.Zanoni. IEEE Trans. Electron Dev. 51, 1554 (2004).

Fecha: viernes, 27 de abril de 2007
Hora: 12:00
Lugar: C-206.1 ETSI Telecomunicación [Cómo llegar]
 
Título: "Precision Chemical Engineering: Creating 3D Nanostructured Surfaces"
Ponente: Jon A. Preece
Organismo: School of Chemistry, University of Birmingham, UK
Resumen:
The lecture will explore how strategies are being developed to integrate the top-down and bottom-up approaches, which will potentially lead to functional three dimensional nanostructured surfaces, using examples from the Preece group laboratory. Examples will include (i) lithographically writing to surfaces with X-rays and electron beams that chemically modify self-assembled monolayers, such that the self-organisation of self-assembled nanoparticles can be realised at the patterned surfaces, and (ii) lithographically writing to surfaces with a scanning near field optical microscope, which are covered with a self-assembled gold nanoparticulate material that upon light irradiation is designed to undergo a chemical reaction to afford a solid gold nanowire. F.P. Gibbons, A.P.G. Robinson, R.E. Palmer, M. Manickam, J.A. Preece, Small, 2006, 2, 1003-1006 S. Sun, P.M. Mendes, K. Kritchley, S.D. Evans, G.J. Leggett, J.A. Preece, Nanoletters, 2006, 6, 345-350. P. Mendes, S. Jacke, Y. Chen, S.D. Evans, K. Kritchley, K. Nikitin, R. E. Palmer, D. Fitzmaurice, J.A. Preece, Langmuir,2004, 20, 3766-3768.

Fecha: viernes, 30 de marzo de 2007
Hora: 12:00
Lugar: C-206.1 ETSI Telecomunicación [Cómo llegar]
 
Título: "Structural characterization of InN-based layers grown on silicon substrates by MBE"
Ponente: Javier Grandal
Organismo: ISOM-UPM
Resumen:
This work reports on the growth and the structural characterization of InN and In-rich (Al,Ga)InN layers by plasma-assisted molecular beam epitaxy (PA-MBE). A series of InN samples were grown on top of a high temperature AlN buffer layer (HT-AlN) using the optimization processes described in previous works to be compared with another series of samples grown directly on bare of Si (111) and Si (001) substrates. When growing nanocolumns, it is observed that samples grown at temperatures close to the onset of InN dissociation may exhibit In segregation to the top of the columns, enhancing the lateral growth and leading to conical or pyramidal shapes. The growth of compact InN close to the dissociation onset results in metallic In droplets formation at the surface together with an increase in surface roughness. Growths of compact AlxIn1-xN films was also performed finding that the growth temperature is even more critical than for the case of compact InN or GaxIn1-xN layers. Structural characterization of the samples was also carried out by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) showing a high crystal quality for both the compact and the columnar material. The presence of a surface electron accumulation layer in InN samples, of uncertain origin, is also a hot topic of discussion in the Nitrides literature. In this current work, current-voltage characteristics were measured by atomic force microscopy on InN nanocolumns with different diameters and an average conductivity was calculated.

Fecha: viernes, 23 de marzo de 2007
Hora: 12:00
Lugar: C-206.1 ETSI Telecomunicación [Cómo llegar]
 
Título: "Noise study in photodiodes based on InGaN/GaN MQW"
Ponente: Alvaro Navarro
Organismo: ISOM-UPM
Resumen:

Fecha: viernes, 16 de marzo de 2007
Hora: 12:00
Lugar: C-206.1 ETSI Telecomunicación [Cómo llegar]
 
Título: "Determination of indium segregation in (Ga,In)(N,As) multi-quantum wells by transmission electron microscopy"
Ponente: Esperanza Luna
Organismo: Paul-Drude-Institut für Festkörperelektronik (Germany)
Resumen:
Transmission electron microscopy (TEM) can be used to determine the composition of quaternary (Ga,In)(N,As) quantum wells (QWs). Through the combined analysis of the chemical sensitive (002) dark-field (DF) images and the lattice resolving high-resolution (HR)TEM images, the N and In concentration profiles along the growth direction can be determined. In particular, this method of analysis evaluates the tetragonal lattice distortion in the layers, which is inferred through a detailed analysis of the HRTEM micrographs. By applying this technique on (Ga,In)(N,As)/GaAs MQWs, we demonstrate how the kinetically limited low temperature-low arsenic flux growth conditions affects the morphological instabilities due to the phase separation tendency, as well as the incorporation of In and N. We find clear evidences of In segregation in the samples grown at Ts = 375 °C under low V/III ratio. The impact of higher growth temperatures on In segregation is masked by the increasing surface roughening during growth and lateral composition fluctuations, whereas increasing the V/III ratio reduces In segregation while maintaining morphologically perfect two dimensional QWs. The In concentration around the center of the QW can be well described by Muraki's model, but the disagreement at the interfaces is apparent. We propose a phenomenological model to describe the interfaces, which, in combination to Muraki's model, results in a perfect description of the complete indium profile. Finally, the analysis of QWs grown under different conditions yields that the broadening at the interfaces of the (Ga,In)(N,As) QWs is triggered by the inherent phase separation tendency of the alloy.

Fecha: viernes, 9 de marzo de 2007
Hora: 12:00
Lugar: C-206.1 ETSI Telecomunicación [Cómo llegar]
 
Título: "ZnO-based semiconductor systems for optical devices"
Ponente: Prof. Jiro Temmyo
Organismo: Research Institute of Electronics, Shizuoka University, Hamamatsu, Japan
Resumen:
ZnO-based material systems have a strong potential for use in semiconductor optical devices because of the bandgap energy of 3.3 eV and the large exciton binding energy of 60meV. We have developed a novel remote plasma enhanced metalorganic chemical vapor deposition system for ZnO-based semiconductor systems and succeeded in the bandgap engineering of ZnO-based alloys. We have demonstrated visible electroluminescence by current injection, which will open the door to ZnO-based nano-photonics research. In addition, a brief introduction on Shizuoka university and its related material will also be addressed.

Fecha: viernes, 23 de febrero de 2007
Hora: 12:00
Lugar: C-206.1 ETSI Telecomunicación [Cómo llegar]
 
Título: "Nuevo Impulso a la I+D+I en Europa: VII Programa Marco"
Ponente: Isidoro Padilla
Organismo: Departamento de Ingeniería Electrónica, ETSI Telecomunicación
Resumen:
Los programas marco (PM) han sido y siguen siendo el principal instrumento de la Unión Europea para financiación conjunta de la investigación en el ámbito europeo. Ademas marcan la estrategia de los progrmas Nacionales y Comunitarios Tras 6 ediciones de los Programas Marco, desde 1984, el nuevo 7º Programa Marco presenta unas novedades sobre los anteriores que lo hacen mas extenso en tematicas y tiempo de ejecución, y mas flexible en cuanto a formulas financiación. Estamos justo en el comienzo del 7º PM, que se inicia en 2007 y se extiende hasta 2013, con un presupuesto de 50.000 Millones de Euros . Ya hay publicados mas de 20 temas abiertos a propuestas que se irán repitiendo en llamadas sucesivas en años posteriores. Pero ahora es el momento de comenzar la participacion preparando propuestas que estén alineadas con las estrategias de investigacion Europeas, Nacionales y Locales. Es necesario conocer los temas, las formulas y los procedimientos de participación para conseguir una participación importante en los planes de I+D+I a nivel Europeo. Los objetivos de la reunión del Viernes dia 16 son: 1.Compartir información de posible interés sobre el VII PM 2.Reflexionar sobre el interés en participar en los proyectos del VII PM 3.Despertar nuevas aficiones por los proyectos internacionales y por preparar propuestas

Fecha: viernes, 16 de febrero de 2007
Hora: 11:45
Lugar: Salón de grados de la ETSI Telecomunicación [Cómo llegar]
 
Título: "Molecular beam epitaxial growth window for high quality (Ga,In)(N,As) quantum wells for 1.55 µm emission"
Ponente: Dr. Fumitaro Ishikawa
Organismo: Paul-Drude-Institut für Festkörperelektronik, Berlín (Alemania)
Resumen:
Quaternary (Ga,In)(N,As) is a material of great interest due to its band gap tunability and large conduction band offset with respect to GaAs. These properties are promising for the realization of low cost 1.55 µm telecommunication lasers on GaAs substrate, which show good performance at high operation temperature. Recently, lasers emitting at wavelengths above 1.5 µm have been realized by molecular beam epitaxy (MBE) using (Ga,In)(N,As) or quinary (Ga,In)(N,As,Sb). However, the growth process of these materials is still not well understood, especially for samples with quantum wells wider than 7 nm and containing large In and N amounts that are required for emission above 1.5 µm. In this report, we focus on the plasma-assisted MBE growth of (Ga,In)(N,As) multiple quantum wells (MQWs) containing 36% In and 4% N, with a low As-pressure and low substrate temperature growth concept. The prospects of this concept are the following: (i) the low growth temperature prevents composition modulations, leading to abrupt heterointerfaces; (ii) the low As pressure allows the introduction of a large amount of N in the layers due to the reduced competition for incorporation of group V elements; (iii) reducing the As pressure counteracts the effect of the low growth temperature, thus improving photoluminescence intensity. The above interpretation was examined by growing a MQW structure consisting of 10 periods (Ga,In)(N,As) /Ga(N,As) MQWs at a substrate temperature of 375°C and V/III BEP ratio of 5. As a result, we obtained high-quality MQWs containing 4.5% N and 35.5% In. To obtain the desired long wavelength emission, we grew three 10-period MQWs with QW widths of 6, 7, or 8 nm. Figure 1 shows a cross-sectional transmission electron microscopy (TEM) image of the MQW with the 8 nm wide QWs. The micrograph shows the regularly stacked 10 QW layers which remain smooth throughout the structure. Figure 2 shows room temperature cathodoluminescence spectra for the series of the MQWs after rapid thermal annealing at 720°C for 60 s. We observe 1.34-1.6 µm emission of narrow linewidth (<50 meV), showing a clear red-shift of the spectral peak position with increasing QW width. The large conduction band offset of 410 meV, estimated from calculations is beneficial for a material system considered for high temperature laser operation.

Fecha: viernes, 1 de diciembre de 2006
Hora: 12:00
Lugar: Sala C-206.1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: "Prospects of group-III nitrides with nonpolar surfaces"
Ponente: Prof. Holger Grahn
Organismo: Paul-Drude-Institut für Festkörperelektronik, Berlín (Alemania)
Resumen:
Nonpolar orientations of the wurtzite crystal structure are important not only for light-emitting devices without internal electric fields, but also for polarization-sensitive devices. GaN films grown along the polar direction (C plane) do not exhibit any in-plane polarization anisotropy. In contrast, unstrained M- and A-plane GaN films, where the c-axis lies in the film plane, already exhibit a significant polarization anisotropy with a degree of linear polarization of one for the A exciton, while it is much smaller for the B and C excitons. However, the values for all three transitions can be increased to their maximum values of one, which corresponds to complete linear polarization, by applying anisotropic strain. The optical polarization anisotropy in GaN films with a nonpolar orientation can be used for polarization-sensitive photodetectors and static as well as dynamic polarization filtering. It has also been applied to achieve polarized emission in (In,Ga)N/GaN light-emitting diodes grown along nonpolar orientations.

Fecha: miércoles, 29 de noviembre de 2006
Hora: 12:00
Lugar: Sala C-206.1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: "The beneficial role of defects in digital radiography"
Ponente: Martin Spaeth
Organismo: Professor Emeritus, University of Paderborn (Alemania)
Resumen:
Defects generated by radiation damage are usually considered as an unwanted deterioration of a material. Not so in digital radiography where they are essential for the generation of digital X ray images. Digital radiography has several advantages compared to the conventional radiography based on silver halide X ray films. Its screens are linear over 5 decades, more sensitive than film and the digital images can be stored, transported and manipulated electronically. Most actual commercial systems use image plates containing storage phosphors of single crystalline BaFBr doped with Eu2+ as an activator. The present understanding of the mechanisms of information storage and digital image formation is discussed. In spite of the widespread use of these image plates there is one disadvantage compared to the conventional X ray film: the spatial resolution is inferior. This disadvantage is potentially overcome by the discovery of a novel screen a few years ago using a transparent glass ceramic as X ray screen. The screen is made of a zircon fluoride glass (ZBLAN) which is doped with Eu2+ and a chloride or bromide and transformed into a transparent ceramic by an appropriate heat treatment. In the ceramic small crystallites of BaBr2:Eu2+ or BaCl2:Eu2+ store the information which can be read out similarly as in the BaFBr:Eu2+ screens. The spatial resolution is far superior to the conventional film systems. The ZBLAN glass ceramics are not only excellent storage phosphors , but can also be made into excellent X ray scintillators. The present understanding of the ZBLAN glass ceramic X ray screens is discussed.

Fecha: viernes, 20 de octubre de 2006
Hora: 12:00
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: "Diamond surfaces: a novel platform for biosensors"
Ponente: José Antonio Garrido
Organismo: WALTER SCHOTTKY INST, UNIV. TECNICA DE MUNICH (Alemania)
Resumen:
Diamond exhibits several special properties, e.g. chemical stability, large electrochemical potential window, and excellent biocompatibility, which make it particularly suitable for biofunctionalization and biosensing. However, interfacing diamond surfaces with organic molecules and bio molecules is still a major challenge before the potential of diamond can be fully exploited in the field of biosensors. In addition, very little is known about the interface between diamond surfaces and aqueous electrolytes. In this contribution, I will firstly survey our work on the characterization of H-terminated and O terminated diamond surfaces in contact with aqueous electrolytes, with especial emphasis on surface charging processes. Our results imply the presence of a negative surface potential resulting from a negatively charged diamond/electrolyte interface. The effect of screening and/or specific adsorption of electrolyte ions, as well as the interfacial water structure will be discussed. Finally, I will present our work on the functionalization of diamond surfaces with bio/organic molecules for the development of diamond-based biochemical sensors. Different routes will be reported for the formation of self-assembled monolayers on diamond surfaces, depending on the surface termination and the type of diamond films. We will show how different proteins and enzymes can be immobilized on activated diamond surfaces and still maintain their enzymatic activity. The fabrication and characterization of Enzyme-Field Effect Transistors and Enzyme-Amperometric sensors based on diamond films will be reported.

Fecha: viernes, 22 de septiembre de 2006
Hora: 12:00
Lugar: Salón de Grados, Edificio Sanz Mancebo, ETSI Telecomunicación. [Cómo llegar]
 
Título: "Introducción a la Spintrónica: ¿Qué podemos hacer en el ISOM?"
Ponente: José L. Prieto
Organismo: ISOM
Resumen:
¿Hemos perdido el carro de la Spintrónica? La electrónica del spin surgió con la magnetoresistencia gigante en 1988. Desde entonces se han estudiado muchos tipos de dispositivos y sistemas. Algunos de ellos están ya tan estudiados que ni en Japón son capaces de sacar más combinaciones de materiales o multicapas. En esta charla se introducirá la spintrónica a un nivel básico, ni resolveré la ecuación de difusión para corrientes polarizadas ni me meteré con el modelo de Jullière: fórmulas una o ninguna. Veremos lo que se ha hecho con una visión histórica y a un nivel que nos permita sacar ideas. Se hará incapié en el futuro de la spintrónica y en lo que queda por hacer: ¿migajas u hogazas? El ISOM ha mostrado interés en hacer spintrónica durante años. El problema suele ser salvar el GAP que separa a veces a los magnéticos de los semiconductores y lo que es más importante: encontrar el tiempo para discutir posibilidades. La idea es tener un coloquio al final de la charla para ver si sacamos algo entre todos: Temas que podemos abordar con nuestra tecnología, qué aparatos de medida necesitamos, etc.

Fecha: viernes, 30 de junio de 2006
Hora: 12:00
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: "Some subtleties of GaN and ZnO based quantum wells and quantum dots"
Ponente: Pierre Lefebvre
Organismo: Directeur de Recherche-CNRS. Groupe d’Etude des Semiconducteurs. Universite Montpellier II, FRANCE
Resumen: [Archivo]
Continuous-wave, time-resolved and spatially-resolved photo-luminescence are commonly used to investigate the properties of confined electron-hole pairs in quantum wells and quantum dots. But quite specific properties are introduced by the presence of strong internal electric fields along the (0001) growth direction of such nano-objects built upon wurtzite GaN or ZnO. In particular, issues related to the screening of such fields, by photo-injection of high densities of electron-hole pairs, will be discussed. The emphasis will be put on the difficulty of measuring correctly, without particular precautions, both the emission energy and radiative lifetime in GaN/(Al,GaN) quantum wells and quantum dots and in ZnO/(Zn,Mg)O quantum wells. A specific procedure will be presented that allowed us to achieve such measurements and, therefore, to determine accurately the value of the internal electric field. In the case of ZnO quantum wells, we have established the presence and the magnitude of such fields, for the first time. In a second part of the talk, results of micro-photoluminescence on GaN/AlN isolated quantum dots will be presented. Spectacular spectral diffusion effects were observed which are, again, related to the presence of internal fields.

Fecha: viernes, 23 de junio de 2006
Hora: 12:00
Lugar: Salón de Grados, Edificio Sanz Mancebo, ETSI de Telecomunicación. [Cómo llegar]
 
Título: "Ion beam analysis of GaN-based heterostructures"
Ponente: Andrés Redondo Cubero
Organismo: Centro de Micro-Análisis de Materiales, Universidad Autónoma de Madrid
Resumen:
High electron mobility transistors (HEMTs) based on GaN heterostructures are one of the most promising devices for high-power, high-voltage microwave applications. On these devices electrical properties are very sensible to element concentrations, and also to lattice defects, impurities, diffusion and interface growth problems. Ion Beam Analysis techniques (IBA) are well proved methods for obtaining structural information of such complex heterostructures. Among the results we have obtained I will focus the talk in elemental composition profiles. Several experiments have been carried out to get a complete characterization of active and passivant layers. Rutherford Backscattering Spectrometry (RBS) and Nuclear Reaction Analysis (NRA) have been employed to determine Al, Ga, and In concentration of AlxInyGa1-x-yN layers, which is a crucial parameter for electron confinement. Elastic Recoil Detection Analysis (ERDA) has been used on SixNy layers to obtain Hydrogen content as well.

Fecha: viernes, 9 de junio de 2006
Hora: 11:30
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: "Aplicación de AES y XPS al estudio de dispositivos electrónicos basados en GaN"
Ponente: Diego Alonso Álvarez
Organismo: Departamento de Física Aplicada, Universidad Autónoma de Madrid
Resumen:
El diseño, construcción y caracterización de dispositivos electrónicos y optoelectrónicos es un proceso complejo que requiere conocer y controlar la influencia de una gran cantidad de variables, desde la pureza y cristalinidad de los materiales utilizados a las temperaturas de los tratamientos aplicados (plasmas, RTA...) pasando por los espesores de las capas depositadas o los tiempos de los distintos subprocesos. Este control implica la utilización de numerosas técnicas de análisis y caracterización de estructuras, en general de muy distinta procedencia y basadas en fenómenos físicos completamente distintos. Dos de estas técnicas, la espectroscopía de electrones Auger (AES) y la espectroscopía de fotoelectrones por rayos X (XPS) destacan por ser de las pocas técnicas capaces de dar información cuantitativa de los elementos presentes en la muestra y del tipo de enlaces que forman, siendo además, sensibles sólo a unas pocas monocapas. En esta charla se introducirán los fundamentos de dichas técnicas, sus ventajas y limitaciones, y en particular se mostrará la aplicación de AES para estudiar los contactos metálicos sobre AlGaN/GaN, deteniéndonos en qué tipo de información nueva nos proporciona esta técnica y cómo podría llegar a utilizarse en el futuro para optimizar el diseño de los dispositivos.

Fecha: viernes, 9 de junio de 2006
Hora: 12:00
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: "Crecimiento por MBE de patrones auto-organizados de GaAs sobre sustratos GaAs(111)B desorientados usando nitruros diluidos"
Ponente: Raquel Gargallo Caballero
Organismo: ISOM
Resumen:
Recientemente, la fabricación de superficies patronadas está siendo usado para demostrar el control en el posicionamiento del crecimiento de nanoestructuras semiconductoras tridimensionales, y en particular de puntos cuánticos. Sin embargo, las técnicas pre-patterning muestran algunas desventajas. En este trabajo, expongo una nueva técnica de hole-patterning in-situ, que consiste en el crecimiento epitaxial por haces moleculares (MBE) de una capa del nitruro diluido GaAsN sobre sustratos GaAs(111)B desorientados 1° y 2° en la dirección [-2 1 1]. Posteriormente, se lleva a cabo el recrecimiento sobre estas superficies patronadas de capas de GaAs con el fin de mejorar la calidad superficial y la homogeneidad de las caracterísitcas de los agujeros que conforman el patrón (tamaño, profundidad,...). Seguidamente, se hizo uso de estas superficies patronadas para el crecimiento de puntos cuánticos de InAs, cuyo crecimiento en este tipo de desorientaciones de sustrato resulta ser de gran dificultad. Finalmente, se expondrán los resultados obtenidos de la caracterización estructural, tanto de los patrones de agujeros como de los puntos cuánticos crecidos sobre tales patrones, junto con el estudio de la dependencia de la morfología de la superficie con algunos parámetros de importancia (desorientación del sustrato, condiciones de crecimiento, ...).

Fecha: viernes, 2 de junio de 2006
Hora: 12:00
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: "FOTÓNICA PARA SEGURIDAD Y DEFENSA: Aplicaciones y tendencias."
Ponente: Jorge Julián Sánchez Martínez
Organismo: Sistema de Observación y Prospectiva Tecnológica de Defensa SDG-TECEN
Resumen:
En nuestra sociedad actual, la Fotónica está presente en nuestras vidas en múltiple y sutiles formas, ayudándonos a mejorar nuestra calidad de vida. De entre estas aplicaciones, se encuentra la de Seguridad y Defensa en sentido más amplio: control de tráfico de mercancias, detección precoz de explosivos, y seguridad aeroportuaria son algunos de los ejemplos donde se vislumbran sus primeras aplicaciones, siendo uno de los sectores industriales de mayor carácter innovativo, y por tanto de gran impacto económico, que pueden encontrarse en la actualidad. El presente seminario pretende dar una visión global de los avances de la Fotónica para la Seguridad y Defensa, junto con sus principales tendencias más prometedoras en términos de Tecnología para Sistemas Avanzados.

Fecha: viernes, 26 de mayo de 2006
Hora: 12:00
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: "Low frequency noise in InGaN/GaN MQW-based photodetector structures"
Ponente: Álvaro Navarro
Organismo: ISOM
Resumen:
Noise characteristics of InGaN/GaN multiple-quantum-well (MQW) photodiodes (PD) and photoconductors (PC) were studied. 1/f-type noise was examined in MQW PDs as a function of reverse bias, In content and temperature. Superposed multilevel Random Telegraph Signal Noise was observed under reverse and forward biases. The dominant presence of this type of noise in MQW PCs seems to indicate that its origin was related to localization effects in the InGaN QWs. Detectivity of the MQW PDs was determined at various voltages for a wide range of temperatures.

Fecha: viernes, 19 de mayo de 2006
Hora: 12:30
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: "SiC, Al2O3 and Si HEMT Structures Characterisation and Processing Impact on AlGaN Surface"
Ponente: Fernando González-Posada Flores
Organismo: ISOM
Resumen:
High electron mobility transistors (HEMTs) based on AlGaN/GaN heterostructures are today the most promising devices for high-power, high-voltage microwave applications.Because the benefits for defence and space systems, a significant research effort is being promoted by various funding agencies worldwide. Despite the significant advances made in GaN technology, to make AlGaN/GaN HEMTs fully commercial, new progress and understanding have to be made in materials quality, device processing and reliability issues. It has been long recognized that the AlGaN/GaN surface plays a key role in Schottky gate formation, control of channel two dimensional electron concentration, behaviour of passivation layers, parasitic gate creation, breakdown voltage optimization, polarization charge compensation, etc. Hence, a better understanding of nitrides surface physical and chemical properties, and their control, is needed to optimize HEMT manufacturing, processing reproducibility and to aid in device reliability studies. In this work, we focused in two main points. First one, the structural characterization of AlGaN/GaN samples on different substrates (SiC, Al2O3 and Si) by Normaski optical microscope, Atomic Force Microscope (AFM), X-Ray Diffraction (XRD), Photoluminescence (PL), Rutherford Backscattering Spectrometry (RBS) and Hg-probe profile. Secondly, the processing impact on the AlGaN surface by X-Ray Photoelectron Spectroscopy. Different, combined and critical surface HEMT device processing treatments are analysed in order to determine the physicochemical surface composition and assess a cleaning procedure.

Fecha: viernes, 12 de mayo de 2006
Hora: 12:00
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: "Research activities of the Institute of Electrical Engineering, Slovak Academy of Sciences, particularly on GaAs-based QWIPs and GaN-based MOSHFETs"
Ponente: Peter Kordoš
Organismo: IEE SAS, Bratislava, Slovakia
Resumen:
A brief description of research activities of the IEE SAS (physics and electrodynamics of superconductors, suoperconductive cryoelectronics, metallic and oxide thin layers, III-V semiconductors) will be presented in general. Research activities and results obtained on III-V semiconductors, particularly on GaAs-based MEMS, GaAs-based X-ray detectors, nonplanar lithography, vector Hall sensor for magnetic microscopy and AFM lithography, will be described. Finally, recent results obtained on AlGaAs/GaAs quantum well infrared detectors (QWIPs) and AlGaN/GaN filed-effect transistors with gate oxide (MOSHFETs) will be presented in detail.

Fecha: miércoles, 10 de mayo de 2006
Hora: 12:00
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: "Láseres de pozo cuántico de InGaAsN/GaAs para comunicaciones ópticas en el infrarrojo"
Ponente: Miguel Montes Bajo
Organismo: ISOM
Resumen:
El cuaternario InGaAsN es un material prometedor para la fabricación de láseres para comunicaciones por fibra óptica. Incorporando pequeñas cantidades de nitrógeno a pozos cuánticos de InGaAs/GaAs se puede aumentar la longitud de onda de emisión de estos materiales hasta alcanzar las ventanas ópticas de 1.3 y 1.5 micras, pero supone un deterioro de las figuras de mérito del láser. Durante este seminario se hará un breve repaso del proceso de fabricación de los láseres basados en pozos cuánticos de InGaAsN/GaAs y se analizará el impacto que el nitrógeno tiene en el funcionamiento de los dispositivos. En particular, se estudiará el impacto de la concentración de nitrógeno en la densidad de corriente umbral y en la eficiencia cuántica externa diferencial. Asimismo se indicarán las líneas de trabajo que se llevan a cabo en la actualidad sobre este material en el Instituto de Sistemas Optoelectrónicos y Microtecnología.

Fecha: viernes, 28 de abril de 2006
Hora: 12:00
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: "Selective etching of lattice matched AlInN/GaN structures for microsystem technology"
Ponente: Eugenio Sillero Herrero
Organismo: ISOM
Resumen:
The current trends in microelectronic devices head for an integration of more functionality on a single chip. Therefore, microsystem technology is gaining interest and an important amount of research effort is devoted to the development of such devices. Nowadays, one may find many different commercial microsystems (namely MEMS), but some of them still exhibit poor performance characteristics, in particular for special applications such as harsh environments, high temperature or outer space, as well as in opto-MEMS. For this reason, it is important to overcome silicon technology in order to produce advanced MEMS. The III-N material system is very attractive for these purposes, since its characteristics suit those required for the aforementioned applications. However, some issues of this material system are important drawbacks which should be solved before the development of III-N MEMS, related to the technology (etching) and the built in stress. In this work an selective etching technology of lattice matched heterostructures is presented. This technology allows the development of modified surface micromachining for the fabrication of low stress III-N MEMS.

Fecha: viernes, 7 de abril de 2006
Hora: 12:00
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: "Ferromagnetismo a temperatura ambiente en GaN dopado con Gd"
Ponente: Lucas Pérez
Organismo: Paul Drude Institut für Festkörperelektronik (Paul Drude Institute for Solid State Electronics), Berlin
Resumen:
Los semiconductores magnéticos basados en GaN han despertado gran interés en los últimos años por la posibilidad de ser ferromagnéticos a temperatura ambiente. El GaN dopado con Gd, además de ferromagnetismo a temperatura ambiente, presenta momento magnético colosal (mayor de 1000 µB/Gd) y anisotropía en el momento magnético, lo que hace de él un material interesante tanto desde el punto de vista teórico como experimental. En la charla presentaremos los resultados obtenidos en el Paul Drude Institut relativos tanto al crecimiento como a las propiedades estructurales, magnéticas y magneto-ópticas de este material.

Fecha: viernes, 31 de marzo de 2006
Hora: 12:30
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: "Caracterización de fotodetectores a alta temperatura"
Ponente: Roberto Cuerdo Bragado
Organismo: ISOM
Resumen:

Fecha: viernes, 24 de marzo de 2006
Hora: 12:00
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: "Magneto-óptica en redes periódicas ferromagnéticas"
Ponente: Ana María Bengoechea Encabo
Organismo: ISOM
Resumen:
Los cambios en la polarización (efecto Kerr longitudinal y polar) o intensidad (efecto Kerr transversal) de la luz reflejada por un material ferromagnético llevan información de su estado de imanación. Cuando lo que tenemos son redes periódicas de elementos magnéticos, los efectos magneto-ópticos pueden estudiarse tanto en la luz reflejada (Magneto-Optic Kerr Effect, MOKE) como en la difractada (DMOKE). El efecto Kerr transversal en el difractado, junto con calculos teóricos o simulaciones, puede servir para determinar procesos de imanación en la red, o propiedades magneto-ópticas de una superficie de rugosidad periódica. En el caso de redes ferromagnéticas sobre películas planas también magnéticas, un acoplo dipolar entre ellas puede inducir una estructura periódica de dominios magnéticos en la película plana, como se confirma por microscopía Kerr.

Fecha: viernes, 17 de marzo de 2006
Hora: 12:00
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: "Filtros Clásicos con Elementos Activos de Ganancia Unidad"
Ponente: Víctor Gracia Verano
Organismo: ISOM
Resumen:
El presente trabajo expone un método sistemático para sintetizar filtros activos con celdas de ganancia unidad mediante una transformación de las topologías clásicas con amplificadores operacionales. El procedimiento de investigación se fundamenta en diseñar y caracterizar a nivel de transistor los componentes activos fundamentales a partir de configuraciones en clase AB referenciadas en la literatura y construir las arquitecturas de tres filtros clásicos: Sallen-Key, MFB y Tow-Thomas, funcionando tanto en modo de tensión como de corriente. Utilizando una tecnología CMOS 0.35µm, se realiza la simulación de configuraciones pasa-banda para distintos valores de ganancia, frecuencia crítica y factor de calidad. Los resultados experimentales muestran la viabilidad de estos sistemas y su flexibilidad de diseño sin necesidad de emplear nuevos algoritmos ni seguidores con elevadas prestaciones, al tiempo que confirman la facilidad de añadir nuevos elementos activos al procesamiento analógico en tiempo continuo.

Fecha: viernes, 10 de marzo de 2006
Hora: 12:00
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: "Plasmas reactivos a baja temperatura: Caracterización y diagnóstico"
Ponente: Isabel Tanarro
Organismo: Instituto de Estructura de la Materia, CSIC
Resumen: [Archivo]
Los plasmas producidos en descargas eléctricas a baja presión son plasmas fuertemente alejados del equilibrio, en los que temperaturas electrónicas muy superiores a 10000 K coexisten con temperaturas del gas próximas a la temperatura ambiente; por ello reciben el nombre de plasmas fríos. Sus peculiares características han permitido el desarrollo de múltiples aplicaciones tecnológicas; entre ellas, la deposición química asistida por plasma (PACVD) o el grabado por plasma ("plasma etching"), esenciales en el campo de la microelectrónica. Los fenómenos que ocurren en los plasmas fríos son muy complejos, sin embargo, con el actual grado de conocimiento de los mismos, es posible ajustar y controlar la composición de las mezclas precursoras y los parámetros de las descargas para optimizar los mecanismos de producción. En esta charla se hará una breve introducción a la física y la química de estos plasmas y se comentarán diversas técnicas utilizadas para su caracterización, así como los criterios básicos necesarios para su diagnóstico.

Fecha: viernes, 17 de febrero de 2006
Hora: 12:00
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación. [Cómo llegar]
 
Título: "Nitride semiconductors: Review on Research Carried on at the Institute of High Pressure Physics and TopGaN (Poland)"
Ponente: Tadek Suski and Mike Leszczynski [CVitae]
Organismo: High Pressure Research Center "Unipress" and TopGaN (Polonia)
Resumen: [Archivo]
The seminar will have the following outline: 1) GaN substrates: progress in the high-pressure growth combined with the hydride vapour phase epitaxy (HVPE): we will show the bulk GaN crystals with dislocation density as low as 100 cm-2 of size about 10 mm, as well as 1-inch wafers with dislocation density 104 cm-2. 2) MOVPE and MBE growth on dislocation-free substrates: we will show advantages and disadvantages of both methods, as well as problems when highly mismatched layers of AlGaN are deposited on bulk GaN substrates. 3) Recent high-power broad-area violet laser diodes: we will show first laser diodes (cw operated to about 100 mA) grown by PA MBE, as well as MOVPE devices (power of 200 mW cw). 4) High-pressure as a tool for examination of nitride semiconductors and optoelectronic devices: the high pressure changes position of the conduction band with respect to localized levels. This effect serves for studies of such levels that play important role in device performance.

Fecha: viernes, 3 de febrero de 2006
Hora: 12:00
Lugar: Sala 206-1 Edificio López Araújo. ETSI de Telecomunicación [Cómo llegar]
 
Título: "Biochemical Analytics with Group-III Nitrides"
Ponente: Dr. Martin Eickhoff
Organismo: Walter Schottky Institut, Technische Universität München
Resumen:
AlGaN/GaN solution gate field effect transistors (SGFETs) bear a great potential as sensor devices for electronic detection of biochemical processes as they combine excellent electronic charactristics with biocompatibility and long term stability in liquid electrolytes. The high signal to noise ration of such devices allows the electronic recording of the activity of living cells. The oxidic surface in electrolyte gives rise to a a high pH-sensitivity when operated in electrolyte solutions. In addition, it allows the chemical functionalization by self assembled silane monolayers and the covalent immobilization of biomolecules. The covalent immobilization of enzymes on the surface of AlGaN/GaN SGFETs is demonstrated and the catalytic activity of the immobilized enzymes is measured. Besides measurement of the long term stability we show that differences in the functionalization process result in a different response of the device to specific substrates.

Fecha: lunes, 23 de enero de 2006
Hora: 17:00
Lugar: Sala C-206-1. Edificio C. ETSI Telecomunicación. [Cómo llegar]
 
Título: "Nanotecnología para los Sectores Aeroespacial y Defensa"
Ponente: Héctor Guerrero Padrón
Organismo: Instituto de Técnica Aeroespacial, Ministerio de Defensa
Resumen:
En los últimos años asistimos al inusitado avance de la Nanotecnología. Ésta empieza a tener incidencia en prácticamente todas las áreas de la Ciencia y la Técnica, en lo que ya se denomina revolución nanotecnológica. Los sectores Aeroespacial y Defensa no sólo se postulan como beneficiarios de la Nanotecnología, sino que fueron los motores de algunos de sus desarrollos iniciales. Se presentan las singulares características de estos sectores, en los que pese a sus elevadas barreras (económicas y tecnológicas), la Nanotecnología ha empezado a asentarse. Se revisan algunas de sus aplicaciones actuales, así como otras previstas, que según todos los analistas, propiciarán en estos sectores una auténtica disrupción.

Fecha: viernes, 20 de enero de 2006
Hora: 12:00
Lugar: Salón de Grados. Edificio Sanz Mancebo. ETSI Telecomunicación. [Cómo llegar]
 
Título: "Microscopía de campo cercano, herramienta clave para la Nanotecnología"
Ponente: Adriana Gil [CVitae]
Organismo: Nanotec
Resumen: [Archivo]
En esta presentación se pretende hacer una introducción a la técnica de la Microscopía de Campo Cercano (SPM), tanto sobre funcionamiento como de sus aplicaciones y potencial. Así mismo se presentarán varios proyectos de desarrollo del microscopio que se están llevando a cabo en el departamento de I+D de Nanotec. Los Microscopios de Campo Cercano (SPM) son una herramienta clave para la nanociencia y por tanto para la nanotecnología. Permiten acceder a resolución atómica y/o nanométrica y presentan grandes ventajas que los hacen fundamentales. Pueden operar en diferente tipo de ambientes, al aire, en líquido, en vacío o en atmósfera de gas o con humedad controlada. Pueden aplicarse para el análisis de una gran variedad de muestras como materiales nanoestructurados, magnéticos, conductores o aislantes, polímeros, muestras biológicas, etc. Otro aspecto del potencial de esta técnica es que permite el estudio de diferentes propiedades de la superficie, entre otras, topografía, morfología, fricción, adhesión, dominios magnéticos, elasticidad o potencial superficial. Además de caracterizar las superficies, con los microscopios de campo cercano es posible litografiar o manipular a escala atómica y/o del nanómetro. Además, permite realizar experimentos específicos para el estudio de propiedades de sistemas nanométricos, como por ejemplo propiedades mecánicas de materiales, o transporte eléctrico en nanohilos como nanotubos de carbono o en hilos moleculares con interés para el campo de la nanoelectrónica. En la presentación se comentarán distintos ejemplos de aplicaciones del microscopio de fuerzas con la intención de mostrar la versatilidad y el potencial de esta técnica.

Fecha: martes, 20 de diciembre de 2005
Hora: 13:00
Lugar: Sala C-206-1. Edificio C. ETSI Telecomunicación. [Cómo llegar]
 
Título: "Crecimiento y caracterización de filtros ópticos de InGaN para su posterior integración en fotodetectores basados en estructuras p-i-n de InGaN/GaN"
Ponente: Juan Pereiro Viterbo
Organismo: ISOM
Resumen:

Fecha: viernes, 16 de diciembre de 2005
Hora: 13:00
Lugar: Sala C-206-1. Edificio C. ETSI Telecomunicación. [Cómo llegar]
 
Título: "Tecnologías Microfluídicas y sus Aplicaciones"
Ponente: Francisco Javier Blanco [CVitae]
Organismo: Ikerlan, Centro de Investigaciones Tecnológicas
Resumen: [Archivo]
Los primeros dispositivos microfluídicos fueron desarrollados a principios de la década de los 90 [1]. Estos dispositivos fueron fabricados utilizando tecnologías planares heredadas de la industria microelectrónica. El campo de aplicación fundamental fue el de la química analítica, siendo inicialmente denominados con el término µTAS (micro-Total Analysis Sytems). El uso de las tecnologías microfluídicas permitió desarrollar dispositivos analíticos más precisos, rápidos y de bajo coste. Durante los últimos años las tecnologías microfluídicas se han desarrollado para otros campos de la química y especialmente de la Biotecnología. Se han desarrollando sistemas más complejos e integrados, lo que ya se conoce como dispositivos Lab-on-a-chip. Estos dispositivos han ido incorporando diferente tecnologías de microsistemas, dotando de una mayor funcionalidad a los mismos y abriendo nuevos campos de investigación. En esta charla se pretende dar un repaso a las diferentes tecnologías microfluídicas con especial énfasis en su evolución hacia nuevos dispositivos fabricados sobre materiales plásticos de bajo coste. Se repasarán algunos ejemplos de dispositivos basados en las diferentes tecnologías microfluídicas.

Fecha: viernes, 2 de diciembre de 2005
Hora: 13:00
Lugar: Sala C-206-1. Edificio C. ETSI Telecomunicación. [Cómo llegar]
 
Título: "III-Nitride research at the Walter Schottky Institut: an Overview"
Ponente: Prof. Martin Stutzmann [CVitae]
Organismo: Walter Schottky Institut, Munich, Germany
Resumen: [Archivo]
This presentation will provide a review of current and future research activities at the WSI related to GaN, AlGaN, and AlN. III-nitride epitaxial films are prepared by plasma-enhanced MBE. Doping of GaN and AlGaN with Si has been investigated systematically with respect to doping efficiency, doping-induced structural changes, and DX behavior. Similarly, Mn as a magnetic impurity in GaN and AlN has been studied extensively with a variety of defect spectroscopy techniques. Heterointerfaces of AlGaN with other widegap semiconductors (diamond, ZnO) are also of current interest. Oxide formation and details of Schottky barriers on GaN and AlGaN are important for many sensor applications of the III-nitrides and are investigated by surface sensitive spectroscopy. Finally, the biofunctionalization of III-nitride surfaces will be discussed in view of future biosensor devices.

Fecha: viernes, 25 de noviembre de 2005
Hora: 12:00
Lugar: Sala C-206-1. Edificio C. ETSI Telecomunicación. [Cómo llegar]
 
Título: "Nuevos Transistores de Nitruros para Aplicaciones a 40, 60 y 94 GHz"
Ponente: Tomás Palacios
Organismo: Electrical and Computer Engineering Department University of California Santa Barbara
Resumen:
Many applications await the development of compact solid-state amplifiers at frequencies above 30 GHz. Satellite transponders, anti-collision car radars, high speed point-to-point wireless transmitters, and highly efficient radars for the navy are only a few of the many civil and military applications that would benefit from these amplifiers in the 30 to 94 GHz range. The basic requirements are common to all these applications: small, reliable, efficient and noise-less solid-state amplifiers to substitute the bulky and unreliable traveling-wave-tube amplifiers currently used at these frequencies. GaN-based high electron mobility transistors (HEMTs) are the most promising option for power amplification at frequencies above 30 GHz. However, three major problems need to be addressed in order to take advantage of the full potential of AlGaN/GaN HEMTs at these frequencies. The first problem is the low electron velocity measured at the AlGaN/GaN heterointerface, which limits the maximum frequency of operation of these devices. The second issue is the fast decrease of f_T and f_max at high drain current levels, which reduces the linearity and large signal gain. Finally, the poor confinement of the 2DEG causes important short channel effects which severely limit the performance of deeply-scaled devices. In this talk, I will describe the different steps that we have followed at UCSB to overcome these problems and maximize the high frequency performance of nitride-based HEMTs. To increase the electron velocity and the 2DEG confinement of GaN-based HEMTs, we have introduced the concept of "dipole engineering" in nitrides. Dipole engineering is a new powerful tool for the device designer. It is based on the use of the extremely high polarization-based electric fields of ultra-thin AlN and InGaN layers grown on GaN to optimize the band diagram of the devices. On the other hand, the understanding of the unique transport properties of nitride semiconductors allows the fabrication of highly linear and stable devices over the whole drain current range. By combining these two approaches, novel GaN-based transistors with record performance at mm-wave frequencies will be presented.

Fecha: jueves, 15 de septiembre de 2005
Hora: 12:30
Lugar: Sala C-206-1. Edificio C. ETSI Telecomunicación. [Cómo llegar]
 
 

 

 

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