Optoelectronic studies in nanocrystalline silicon Schottky diodes obtained by Hot-Wire Chemical Vapour Deposition

The very usual columnar growth of nanocrystalline silicon leads to electronic transport anisotropies. Whereas electrical measurements with coplanar electrodes only provide information about the electronic transport parallel to the substrate, it is the transverse transport which determines the collection efficiency in thin film solar cells. Hence, Schottky diodes on transparent electrodes were obtained by hot-wire CVD in order to perform external quantum efficiency and surface photovoltage studies in sandwich configuration. These measurements allowed to calculate a transverse collection length, which must correlate with the photovoltaic performance of thin film solar cells. Furthermore, the density of charge trapped at localized states in the bandgap was estimated from the voltage dependence of the depletion capacitance of these rectifying contacts.

Compositional influence on the electrical performance of zinc indium tin oxide transparent thin-film transistors

In this work, zinc indium tin oxide layers with different compositions are used as the active layer of thin film transistors. This multicomponent transparent conductive oxide is gaining great interest due to its reduced content of the scarce indium element. Experimental data indicate that the incorporation of zinc promotes the creation of oxygen vacancies. In thin-film transistors this effect leads to a higher threshold voltage values. The field-effect mobility is also strongly degraded, probably due to coulomb scattering by ionized defects. A post deposition annealing in air reduces the density of oxygen vacancies and improves the fieldeffect mobility by orders of magnitude. Finally, the electrical characteristics of the fabricated thin-film transistors have been analyzed to estimate the density of states in the gap of the active layers. These measurements reveal a clear peak located at 0.3 eV from the conduction band edge that could be attributed to oxygen vacancies.

La presencia de la mujer en la poesía de José Agustín Goytisolo

El 19 de marzo del pasado año 2009 se cumplieron diez años de la muerte de José Agustín Goytisolo. Con este motivo se han sucedido los homenajes y congresos que se han ocupado de estudiar su poesía y de repasar su legado desde ángulos muy diversos. Este artículo aspira también a rellenar un hueco que –sorprendentemente o no– no ha merecido hasta el presente especial atención: la presencia de la mujer en la poesía goytisoliana. Mi objetivo es trazar una panorámica del lugar que las mujeres ocupan en sus versos y mostrar que en su gran mayoría son diferentes de las figuras femeninas que pueblan la tradición literaria. En primer lugar porque, desde el punto de vista de la enunciación, la voz poética no se apropia de la mujer convirtiéndola en objeto de contemplación, sino que, en general, es sujeto de la historia en paridad con el poeta. En segundo lugar, porque las mujeres goytisolianas tampoco se ajustan a los “códigos” a los que las ha relegado el discurso patriarcal: tienen vida propia y no funcionan como símbolo de aspiraciones ajenas ni como proyección del imaginario masculino.

Electronic transport in low temperature nanocrystalline silicon thin-film transistors obtained by Hot-Wire CVD

Hydrogenated nanocrystalline silicon (nc-Si:H) obtained by hot-wire chemical vapour deposition (HWCVD) at low substrate temperature (150 °C) has been incorporated as the active layer in bottom-gate thin-film transistors (TFTs). These devices were electrically characterised by measuring in vacuum the output and transfer characteristics for different temperatures. The field-effect mobility showed a thermally activated behaviour which could be attributed to carrier trapping at the band tails, as in hydrogenated amorphous silicon (a-Si:H), and potential barriers for the electronic transport. Trapped charge at the interfaces of the columns, which are typical in nc-Si:H, would account for these barriers. By using the Levinson technique, the quality of the material at the column boundaries could be studied. Finally, these results were interpreted according to the particular microstructure of nc-Si:H.

Microcrystalline silicon thin film transistors obtained by Hot-Wire CVD

Polysilicon thin film transistors (TFT) are of great interest in the field of large area microelectronics, especially because of their application as active elements in flat panel displays. Different deposition techniques are in tough competition with the objective to obtain device-quality polysilicon thin films at low temperature. In this paper we present the preliminary results obtained with the fabrication of TFT deposited by hot-wire chemical vapor deposition (HWCVD). Some results concerned with the structural characterization of the material and electrical performance of the device are presented.

Thin Film Transistors obtained by Hot-Wire CVD

Hydrogenated microcrystalline silicon films obtained at low temperature (150-280°C) by hot wire chemical vapour deposition at two different process pressures were measured by Raman spectroscopy, X-ray diffraction (XRD) spectroscopy and photothermal deflection spectroscopy (PDS). A crystalline fraction >90% with a subgap optical absortion 10 cm -1 at 0.8 eV were obtained in films deposited at growth rates >0.8 nm/s. These films were incorporated in n-channel thin film transistors and their electrical properties were measured. The saturation mobility was 0.72 ± 0.05 cm 2/ V s and the threshold voltage around 0.2 eV. The dependence of their conductance activation energies on gate voltages were related to the properties of the material.

Microdoping compensation of microcrystalline silicon obtained by Hot-Wire Chemical Vapour Deposition

Undoped hydrogenated microcrystalline silicon was obtained by hot-wire chemical vapour deposition at different silane-to-hydrogen ratios and low temperature (<300 °C). As well as technological aspects of the deposition process, we report structural, optical and electrical characterizations of the samples that were used as the active layer for preliminary p-i-n solar cells. Raman spectroscopy indicates that changing the hydrogen dilution can vary the crystalline fraction. From electrical measurements an unwanted n-type character is deduced for this undoped material. This effect could be due to a contaminant, probably oxygen, which is also observed in capacitance-voltage measurements on Schottky structures. The negative effect of contaminants on the device was dramatic and a compensated p-i-n structure was also deposited to enhance the cell performance.

¿Cómo se siente? Llaves propioceptivas de la inteligencia emocional

La propiocepción juega un papel crucial tanto en la expresión como en la percepciónde las emociones. Estado emocional propioceptivo se manifiesta en la postura, los gestos,las expresiones faciales y el tono de voz siendo fuente de información objetiva del estado deánimo personal. Si le preguntamos a la persona: "¿Cómo se siente?" y le responden: " Bien,gracias ", pero captamos tristeza en su voz y observamos los hombros caídos, creemos más enlas claves propioceptivas que nos proporciona esta información que las palabras. Por esta razón,se presta más atención a la conducta no verbal durante la comunicación con otras personaspara entender el estado real del estado de ánimo. Las emociones pueden expresarsetambién por los movimientos corporales en los artistas profesionales, bailarines y cantantesque sería imposible sin la propiocepción. Nuestros sentimientos hacía las personas estimadasse trasmiten por la disposición motora que está a la base del afecto y es más importante quelas palabras pronunciadas. Por otra parte, la propiocepción es un instrumento importante en laadquisición de nuevos hábitos, habilidades y experiencia profesional como el conocimiento“incorporado”. Siendo la base de las diferencias individuales y la personalidad, constituyendo ala formación y los cambios de carácter, debidos a la repetición múltiple de nuevos (constructivos)hábitos con el fin de sustituir los antiguos (destructivos). La relación entre emociones y elequilibrio corporal referente a la salud fue descrita por investigadores recientes y clásicos con un interés del tratamiento de la persona como una unidad.

Arduino Tricorder : Aplicació Android per a la supervisió, control i adquisició de dades d'una placa Arduino

Aplicació Android per a la supervisió, control i adquisició de dades d'una placa Arduino que disposi de comuninació Ethernet i/o Wi-Fi. Creació d'interfícies dinàmiques amb diferents modalitats d'interacció: tàctil, reconeixement de veu i síntesi de veu.

Lyra Viol “Instrument de música domèstica”

El propòsit d'aquest treball és donar a conèixer la lyra viol i la seva música. Entre d'altres maneres de tocar aquest instrument, mostrar com aquest servia per acompanyar la veu, així com arranjar peces polifòniques tal i com trobem en publicacions de l'època. I serà a partir d'aquests exemples, que he fet els meus propis arranjaments per a viola de gamba i que incloc en aquest treball.