1,721,231 research outputs found
Wide Bandgap Semiconductors for MEMS and Related Process Technologies
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Point Defects Investigation of High Energy Proton Irradiated SiC p+-i-n Diodes
No full textWe performed deep level transient spectroscopy (DLTS), in capacitance, constant capacitance and current mode, on 5 MeV proton irradiated 4H-SiC p+-i-n diodes. The study has revealed the presence of several majority and minority traps, ranging in the 0.4-1.6 eV below the conduction band edge and in the 0.4-1.5 eV above the valence band edge. We present a comparison of the results obtained with the three modes and discuss the nature of the detected traps, in the light of previous results found in the literature. At last, the impact of the irradiation on the minority carrier lifetime is evaluated by electrical measurements
RTCVD synthesis of carbon nanotubes and their wafer scale integration into FET and sensor processes
Get PDFDescripció del recurs: el 1 setembre 2011Los nanotubos de carbono (CNTs, carbon nanotubes) son moléculas tubulares cuyo diámetro es de escala nanométrica y cuyas paredes están formadas por capas monoatómicas de carbono. Su estructura en combinación con su morfología unidimensional confieren unas propiedades muy especiales que hacen de los CNTs un material muy atractivo para el desarrollo de amplia gama de aplicaciones. En el marco de la micro y nanotecnología, los CNTs son un material muy prometedor para la fabricación de dispositivos y sistemas, por ejemplo, en el campo de la nanoelectrónica, los sensores o los sistemas nanoelectromecánicos (NEMS, del inglés nanoeletcromechanical systems). Sin embargo, dado que aún no se han estandarizado procesos para su síntesis controlada, su integración sigue siendo un reto. Esta tesis fue concebida para avanzar en la integración CNTs en distintos micro y nanodispositivos. El trabajo realizado aborda la ingeniería de procesos, el diseño de dispositivos, y la fabricación y la caracterización de esos dispositivos. Se plantearon dos objetivos principales. El primero fue el adquirir el conocimiento de la síntesis de CNTs mediante la técnica de depósito químico desde fase vapor por calentamiento rápido (RTCVD, rapid termal chemical vapour deposition) y desarrollar procesos para la síntesis de CNTs de una estructura concreta y en una determinada configuración. El segundo objetivo fue el desarrollo de procesos de fabricación para la integración de CNTs en dispositivos basados en diferentes tecnologías y con diferentes funcionalidades. A pesar de la problemática inherente al desarrollo de los procesos tecnológicos, se cumplieron la mayor parte de los objetivos inicialmente propuestos. La síntesis de CNTs se logró mediante catalizadores convencionales (principalmente hierro y níquel) y mediante catalizadores no convencionales (platino). Cabe destacar que los procesos de síntesis de CNTs fueron estandarizados a nivel de obleas de 4 pulgadas, tanto para configuraciones de baja densidad de CNTs monocapa (SWCNTs, single-walled carbon nanotubes) como para configuraciones de alta densidad de CNTs multicapa (MWCNTs, multi-walled carbon nanotubes), ya que la síntesis tradicionalmente se realiza a nivel de chip. En cuanto a la integración de CNTs, se optimizaron dos procesos principalmente. Por un lado, se desarrolló una tecnología para la fabricación masiva en oblea de transistores basados en SWCNTs. Mediante esta tecnología se logró la fabricación de 10.000 transistores funcionales en obleas de 4 pulgadas. Por otro lado, se integró gran densidad de MWCNTs sobre los electrodos metálicos de dispositivos que habían sido demostrados para detección bio-electroquímica. La caracterización de estos electrodos demostró que esta actualización de la tecnología mejora el rendimiento de la fabricación y las características electroquímicas de los electrodos respecto a los diseños anteriores. Los resultados presentados en esta tesis son un paso adelante para la Integración a muy gran escala (VLSI, very large system integration) de CNTs. Los procesos que se desarrollaron son de interés en el campo de la nanoelectrónica, en el campo de la bio-sensores electroquímicos, para la fabricación de dispositivos optoelectrónicos y para la fabricación de NEMS.Carbon nanotubes (CNTs) are tubular molecules which diameters may be smaller than one nanometre and which walls are formed of single carbon atom layers that are arranged in a honey comb lattice. Because of their one dimensional aspect ratio and properties, which are conferred by their structural arrangement, CNTs are a very attractive material for a wide range of applications. In the frame of micro- and nanotechnology, CNTs have been demonstrated to be very promising for the fabrication of devices and systems for nanoelectronics, sensors or nanoelectromechanical systems (NEMS). However, standardised processes for their fully controlled synthesis and their successful integration into those systems are still challenging. This thesis was conceived to advance on the wafer scale integration of CNTs into micro- and nanodevices. Performed work dealt with process engineering, device design, device fabrication and device characterization. Two major goals were pursued: (i) to acquire the knowhow on the synthesis of CNTs by rapid thermal chemical vapour deposition (RTCVD) to develop recipes to synthesize certain in structure CNTs and certain in morphology CNT arrays, and (ii) the wafer scale integration of CNTs into devices with different functionalities and technological processes by conventional fabrication steps. Despite the inherent problematic of the technological process developments, most of the initially foreseen goals were fulfilled. The CNT synthesis was achieved by conventional (mainly iron and nickel) and by nonconventional (platinum) catalyst materials. It is remarkable how the CNT RTCVD synthesis processes were standardized at 4 inch wafer scale for either low density of single-walled (SW) CNT arrays or for dense, vertically aligned multi-walled (MW) CNT arrays, since the CNT synthesis is normally performed at chip level. Regarding the wafer scale integration of the CNTs, two main processes were optimised. On the one side, SWCNTs were integrated in the fabrication of CNT-FETs. This technology resulted in the fabrication of 10,000 functional CNT-FETs on 4 inch wafers in a sole fabrication process. Later on, the technology was upgraded for the fabrication of passivated CNT-FET devices for electrochemical sensing. On the other side, dense arrays of MWCNTs were integrated into devices based on metallic electrodes that had previously been demonstrated for bio-electrochemical sensing. These electrodes were demonstrated to improve the fabrication yield and the electrochemical characteristics with respect to the previous designs. Presented in this thesis results are a step forward to the Very Large Scale Integration (VLSI) of CNTs. The developed processes are of interest in the field of nanoelectronics, in the field of bio-electrochemical sensing, for the fabrication of optoelectronic devices and for the fabrication NEMS
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Method for exfoliating and transferring graphene from a doped silicon carbide substrate to another substrate
No full textLa presente invención se refiere a un procedimiento de exfoliación y transferencia de grafeno de un sustrato de carburo de silicio dopado a otro sustrato, donde dicho procedimiento se basa en su exfoliación inducida por el burbujeo de hidrógeno que se produce en la electrolisis del agua. [ES]The present invention relates to a method for exfoliating and transferring graphene from a doped silicon carbide substrate to another substrate, the method being based on exfoliation induced by hydrogen bubbles produced in the electrolysis of water. [EN]Peer reviewedConsejo Superior de Investigaciones Científicas (España), Centro de Investigación Biomédica en Red (CIBER)A1 Solicitud de patente con informe sobre el estado de la técnic
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Novel materials and processes for gate dielectrics on silicon carbide
Get PDFConsultable des del TDXTítol obtingut de la portada digitalitzadaThere is considerable evidence of the need for a semiconductor technology which exceeds the limitations imposed by silicon across a wide spectrum of industrial applications. Wide bandgap semiconductor, such as silicon carbide (SiC), gallium nitride (GaN) and diamond, offer the potential to overcome both the temperature and voltage blocking limitations of Si. SiC is nowadays the most attractive candidate, offering significant potential advantages at both high temperature and high voltage levels whilst benefiting from tractable materials technology. Moreover, SiC is the only that can be thermally oxidized to form a high quality native oxide (SiO2), which enables the fabrication of MOS based devices. However, very near the definitive emergence, the SiC technology needs to address two fundamental limitations: The price of the wafers and the poor SiC/SiO2 interface. The high density of imperfections encountered at the SiC/oxide interface represents a major obstacle in the development of functional SiC devices. The main efforts of this thesis have been directed to the detection and reduction of interface traps in the oxide/SiC interface. To achieve this demanding objective, two different ways have been contemplated: (1) Investigations have been carried out to improve the thermal oxidation or even to improve the formation of the interface with alternative techniques as nitridation or deposited oxides. (2) The classical insulator made up with SiO2 has been replaced by other innovative dielectrics. Innovative gate fabrication processes have been proposed in this thesis using deposited SiO2 gate oxides from PECVD with silane and TEOS as precursors. SiO2-TEOS deposited oxides are an alternative to thermal oxidation. 4H-SiC MOSFET with mobilities up to 38-45 cm2/Vs [(0001) face] and 216 cm2/Vs [(11-20) face] have been fabricated. We have demonstrated that the thermal oxidation of Ta2Si is a simple way to achieve a high-k dielectric on SiC (and on Si). We have fabricated one of the first well behaved high-k MOSFET on SiC with a mobility peak up to 45 cm2/Vs In the last section, a field-effect mobility model including Coulomb scattering at interface traps has been proposed fitting the experimental channel mobility of SiC MOSFETs and the device behavior depending on the density of interface traps, the substrate doping level and the temperature
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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