Plataforma hardware universal para prácticas sobre sistemas electrónicos analógico-digitales avanzados en régimen de semipresencialidad

Aquest projecte tracta d’implementar una metodologia per fer pràctiques d’Electrònica Analògica amb circuits avançats que es puguin configurar fàcilment dins d’una placa hardware universal. Aquesta metodologia es basa en el procés habitual que segueixen els dissenyadors electrònics i consta de tres fases: 1- disseny i càlcul teòric del circuit 2- simulació del circuit 3- mesures sobre un prototip 4- validació del disseny Aquest procés s’ha de fer seqüencialment i estaria controlat per un programa web que donaria als estudiants el timing correcte de les tasques a realitzar i els ajudaria amb els continguts teòrics necessaris. El fet de que el programa sigui web facilita la semipresencialitat de les sessions de laboratori i permet una gran millora a l’autoaprenentatge dels estudiants. Tant el software que controla la metodologia com el material de pràctiques es transferible a qualsevol assignatura que faci pràctiques de circuits analògics

VIRUP "En busca de los viral"

Este trabajo es la idea llevada a la práctica, de cuatro amigos, compañeros y alumnos del Grado de Publicidad y Relaciones Públicas de la Universidad de Valladolid. Todo comenzó en una asignatura de segundo de carrera, en la que se nos proponía realizar un proyecto relacionado con las nuevas tecnologías. Nosotros no quisimos quedarnos en lo convencional, y fuimos más allá. Así es como nació VIRUP: “En busca de lo viral”. La organización de eventos es una de las salidas profesionales que más nos ha llamado la atención desde que comenzamos la carrera, es por ello que quisimos crear algo nuevo y diferente, que fuera por y para alumnos. Durante las tres ediciones, el principal objetivo ha sido ofrecer a nuestros compañeros contenidos de calidad sobre redes sociales, a través de profesionales del sector. En definitiva, poder generar conocimiento e ideas sobre el mundo digital, que en un futuro les fuesen útiles laboralmente.Departamento de Historia Moderna, Contemporánea y de América, Periodismo y Comunicación Audiovisual y PublicidadGrado en Publicidad y Relaciones Pública

Low temperature oxide desorption in GaAs (111)A substrates

The aim of this work is to study oxide removal processes on GaAs (111) A substrates previous to epitaxial growth. We have studied conventional thermal desorption and processes based on the reduction of surface oxides by deposition of gallium, indium and exposure to atomic hydrogen. We have determined substrate temperatures (Ts) for optimum oxide removal in epi-ready substrates by the different studied processes: Ts = 540 °C for thermal desorption, Ts = 505 °C for indium deposition and Ts = 400 °C for oxide desorption by exposure to atomic hydrogen. All these processes allow for a subsequent good quality epitaxial growth. These results cannot be directly extended to oxide removal in grown samples that have been exposed to air outside the growth chamber. In this case, we have found that only indium deposition and exposure to atomic hydrogen are compatible with regrowth processes.We acknowledge financial support from Spanish MINECO (Grant TEC2011-29120-C05-04), and CAM (Grant S2009ESP-1503). Jesús Herranz acknowledges the JAE program for the funds.Peer Reviewe

Direct formation of InAs quantum dots grown on InP (001) by solid-source molecular beam epitaxy

We have developed a growth process that leads to the direct formation of self-assembled InAs quantum dots on InP(001) by solid-source molecular beam epitaxy avoiding the previous formation of quantum wires usually obtained by this technique. The process consists of a periodically alternated deposition of In and As correlated with InAs(4×2)(2×4) surface reconstruction changes. Based on the results obtained by in situ characterization techniques, we propose that the quantum dots formation is possible due to the nucleation of In droplets over the InAs(4×2) surface during the In deposition step and their subsequent crystallization under the As step.The authors acknowledge the financial support of the Spanish MICINN (TEC2008-06756-C03-01), Consolider-QOIT (CSD2006-0019), and CAM (S-505/ESP/000200). P.A.G. and A.R. thank the I3P program. B.A. thanks the Ramón y Cajal program.Peer reviewe

Study of Growth Parameters for Single InAs QD Formation on GaAs(001) Patterned Substrates by Local Oxidation Lithography

This work studies the selective nucleation of InAs within nanoholes on GaAs(001) substrates patterned by atomic force microscopy local oxidation. The effects of substrate temperature and As4 overpressure during InAs deposition directly on the patterned substrate (without a GaAs buffer layer) are considered. It is found that when InAs is deposited at substrate temperature of 510 °C under low As4 overpressure, a single InAs quantum dot per nanohole is obtained for a broad range of sizes of pattern motifs. The use of these InAs quantum dots as seed nuclei for vertical stacking of optically active single InAs site-controlled quantum dots is investigated.The authors acknowledge financial support by Spanish MINECO through Grants ENE2012-37804-C02-02 and TEC2011-29120-C05-04. Jesús Herranz acknowledges the JAE program for funds.Peer reviewe

Interleaving and switching pattern modulation to conducted EMI reduction

This paper explores new techniques to reduce the conducted EMI generated by switched power converters operating in multiconverter arrangement. These techniques are based in the combined application of interleaving and the modulation of some characteristics of the switching patterns. The effectiveness of such methods in terms of EMI reduction is theoreticaly developed and experimentally validated in a four channel parallel buck converter operating in closed loop. The technique that provides the best attenuation results is identified. Finally, undesired sideeffects produced by these techniques, such as an increase in the output voltage ripple, are evaluated.Peer ReviewedPostprint (published version

Role of re-growth interface preparation process for spectral line-width reduction of single InAs site-controlled quantum dots

We present growth and optical characterization measurements of single InAs site-controlled quantum dots (SCQDs) grown by molecular beam epitaxy on GaAs (001) patterned substrates by atomic force microscopy oxidation lithography. InAs SCQDs directly grown on the patterned surface were used as a seed layer and strain template for the nucleation of optically active single InAs SCQDs. The preservation of the initial geometry of the engraved pattern motifs after the re-growth interface preparation process, the lack of buffer layer growth prior to InAs seed layer deposition and the development of suitable growth conditions provide us an improvement of the SCQDs' active layer optical properties while retaining a high ratio of single occupation (89%). In this work a fivefold reduction of the average optical line-width from 870 μeV to 156 μeV for InAs SCQDs located 15 nm from the re-growth interface is obtained by increasing the temperature of the initial thermal treatment step of the re-growth interface from 490 °C to 530 °C.The authors thank financial support by Spanish MINECO through grants ENE2012-37804-C02-02 and TEC2011-29120-C05-04. Jesús Herranz acknowledges the JAE program for the funds.Peer reviewe

Low temperature oxide desorption in GaAs (111)A substrates

Trabajo presentado al 17th european Molecular Beam Epitaxy Workshop celebrado en Levi (Finlandia) del 10 al 13 de Marzo de 2013.Peer Reviewe

III-V semiconductor quantum dots for efficient quantum light sources

Comunicación presentada en el 3rd international Workshop Engineering of quantum emitter properties, celebrado en Linz (Austria) el 17 y 18 de diciembre de 2015.Photonic crystal microcavities (PCMs) with embedded quantum dots (QDs) have been shown as excellent test bed systems for experiments in the field of cavity quantum electrodynamics (c-QED) that may open doors to efficient quantum photonic devices for the generation of single-photons, entangled photon pairs and ultra-low threshold lasing. Based on fundamental excitonic emission and on biexciton-exciton recombination cascade, a single QD embedded in a PCM become efficient emitters of single photons or entangled photon pairs provided that both spectral and spatial matching of the optical cavity mode and the optical emission of the single nanostructure occur. Within this approach, we have explored several systems and growth methods with the aim of fabricating QD which fulfil the requirements for an efficient coupling between a single QD and a PCM. We have fabricated QD by molecular beam epitaxy (MBE) using a) droplet epitaxy and b) selective nucleation at nano-holes fabricated by atomic force microscopy local oxidation (AFMLO) lithography. Results will be presented of QD in GaAs/AlGaAs(111)A, InAs/GaAs(001) and InAs/InP (001). With the aim of obtaining coupled QD-PCM, we have followed two procedures: one is based on the fabrication of a PCM around a buried QD whose position and wavelength emission are previously determined; the other approach consists of locating a single QD by using AFMLO, at the maximum of the electric field of a prefabricated PCM. A MBE re-growth procedure has been developed for completing the PCM membrane thickness.Peer Reviewe