1,720,973 research outputs found
Gettering Technology Based on Porous Silicon
No full textThis paper briefly reviews a gettering technology based on porous silicon (PS). PS layers shown to have effective gettering properties for fast-diffusing impurities. Samples saturated with Au or Cu on which the PS layer made on the wafer backside, increases the generation lifetime of minority carriers from 0.05 - 0.1 mus to - 0.5 mus. The PS getter is demonstrated to be located either on the wafer backside or on the front side underneath an epitaxial layer. When formed on the wafer backside, the PS getter may be readily removed together with the absorbed impurities after the gettering process. When fabricated on the wafer front side underneath the epitaxial layer, the getter is brought closer to the wafer working regions as much as possible to provide the most effective gettering effect. At the same time, the epitaxial layer protects chemically active PS against all chemical attacks during the device manufacturing. The buried PS getter may be designed as either a continuous or discontinuous layer configured as, for example, a pattern of isolating regions in VLSI. When property adapted to the produced device conditions, the buried PS getter is shown to withstand successfully the whole VLSI production run providing advanced gain characteristics
Bending properties in oxidized porous silicon waveguides
Get PDFThe greatest limit in high-speed communications between different circuit blocks is due to the delays introduced by metal interconnections. Knock-down wire communication bottleneck is, therefore, one of the best goals that current research could reach in the held of fast electronics. A possible solution is to build fast optical links and even better if the technology is based on silicon. To attain these ends, we have made studies into possibility to fabricate optical waveguide based on oxidized porous silicon. In the last few years, such a device: was realized and characterized. Waveguiding in the visible and in the near infrared was demonstrated, With propagation losses of about 3-5 dB/cm for a light with a wavelength of 632.8 nm. Moreover, a design feature of an integrated waveguide based on oxidized porous silicon is that it offers a spontaneous bending of the waveguiding layer at its ends. The edge bending is provided by a convex camber of a leading edge of forming porous silicon. This bending can be exploited to promote a vertical light output with no use of any additional devices. The paper discusses the properties of edge bending, evaluation of the light losses depending on the radius of curvature, and analysis of possibilities to reduce these losses. (C) 2001 Elsevier Science Ltd. All rights reserved
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
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
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
Fine Structure of photoluminescence spectra from Erbium incorporated with Iron in oxidised porous silicon
No full textWe report 77 K Photoluminescence (PL) and Photoluminescence Excitation (PLE) spectroscopies of Er ions incorporated with Fe in oxidized porous silicon (OPS) in the form of 5–50 nm sized clusters containing Fe, O, and Er. Twenty sharp (FWHM of about 0.4 meV) PL s peaks related to the transitions between highly split levels of 4I13/2 and 4I15/2 multiplets were observed. Two different Er centers having cubic and lower than cubic symmetries were identified. The photoluminescence excitation spectrum of the 1533 nm PL peak comprises no resonant features but a broad band spanning from 300 to 570 nm. The mechanism of excitation of Er ions through Fe : O : Er nanoclusters in the OPS host is presented
X-ray diffractometry of Si epilayers grown on porous silicon
Get PDFX-ray double-crystal diffractometry was used to measure lattice deformation of porous silicon (PS) and Si epitaxial layers grown on PS. PS layers 1-10 μm in thickness and 15-65% in porosity were formed by anodization of n+-type Sb doped Si wafers in a 12% HF aqueous solution. Lattice deformations of both PS and epitaxial layers are shown to strongly depend on PS porosity. Grown on uniform PS 40-60% in porosity, the epilayers, single-crystal as they are, display high lattice deformation and defect density. Epilayers grown on two-layer PS are comparable with the films grown on the n+-type single-crystal Si substrate. © 2002 Published by Elsevier Science B.V
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