1,721,007 research outputs found
Fluorine in Ge: Segregation and EOR-defects stabilization
No full textIn this paper we investigate the F behavior in Ge during solid phase epitaxy (SPE) and post-SPE annealing. Fluorine implanted with a fluence of 1 x 10(15) F/cm(2) and an energy of 35 key induced the formation of an amorphous Ge layer. Detailed chemical and structural characterizations of the as implanted and annealed samples evidenced a strong segregation of F at the moving amorphous/crystalline interface, leading to a remarkable SPE rate retardation. In addition, we observed that F accumulates in correspondence of the end of range (EOR) defects. The comparison between the thermal evolution of damage produced by self-implantation and F implantation in Ge suggests that F increases significantly the stability of EOR. Such behavior clarifies the role of F in modifying the As diffusion in Ge recently reported in literature. (C) 2011 Elsevier B.V. All rights reserved
Mechanism of boron diffusion in amorphous silicon
Full text linkWe have elucidated the mechanism for B migration in the amorphous (a-) Si network. B diffusivity in a-Si is much higher than in crystalline Si; it is transient and increases with B concentration up to 2x10(20) B/cm(3). At higher density, B atoms in a-Si quickly precipitate. B diffusion is indirect, mediated by dangling bonds (DB) present in a-Si. The density of DB is enhanced by B accommodation in the a-Si network and decreases because of a-Si relaxation. Accurate data simulations allow one to extract the DB diffusivity, whose activation energy is 2.6 eV. Implications of these results are discussed
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Formation of Hybrid Silicon Nanostructures via Capillary Instability Triggered in Inductively-Coupled-Plasma Torch Synthesized Ultra-Thin Silicon Nanowires
No full textThis paper provides a report on the formation of two main classes of hybrid silicon nanostructures via the capillary instability induced in ultra‐thin silicon nanowires (SiNWs) when subject to high temperature annealing. The first class of hybrid Si nanostructures shows a high‐level nanostructural order, and regroups (i) periodic strings of almond‐shaped Si nanocrystals (SiNCs) having average dimension of 3 nm and connected by ultra‐thin (≈2 nm) SiNWs and (ii) spherical SiNC chains (mean diameter of 6 nm, spaced averagely by 16 nm), both embedded into silica NWs. In the second class of hybrid Si nanostructures, the SiNCs have different dimensions (in the 3–14 nm size range) and shapes, or a modulated Si core inside a SiO2 shell, thus exhibiting much higher nanostructural complexity. The self‐assembly of such nanostructures is related to the gas ambient under which the thermal treatment is performed. However, by increasing the annealing temperature, the SiNWs’ cores preferentially evolve toward the spherical SiNC chain morphology. The ultra‐thin diameter (2–3 nm) of the initial SiNWs is a key feature to induce the hybrid Si nanostructures formation. This study opens up the prospects of in situ controlling the formation of Si nanocrystals inside silica NWs, which will lead to the tailoring of their optoelectronic properties
Growth Mechanisms of Inductively-Coupled Plasma Torch Synthesized Silicon Nanowires and their associated photoluminescence properties
No full textUltra-thin Silicon Nanowires (SiNWs) were produced by means of an industrial inductively-coupled plasma (ICP) based process. Two families of SiNWs have been identified, namely long SiNWs (up to 2-3 micron in length) and shorter ones (~100 nm). SiNWs were found to consist of a Si core (with diameter as thin as 2 nm) and a silica shell, of which the thickness varies from 5 to 20 nm. By combining advanced transmission electron microscopy (TEM) techniques, we demonstrate that the growth of the long SiNWs occurred via the Oxide Assisted Growth (OAG) mechanism, while the Vapor Liquid Solid (VLS) mechanism is responsible for the growth of shorter ones. Energy filtered TEM analyses revealed, in some cases, the existence of chapelet-like Si nanocrystals embedded in an otherwise silica nanowire. Such nanostructures are believed to result from the exposure of some OAG SiNWs to high temperatures prevailing inside the reactor. Finally, the intense photoluminescence (PL) of these ICP-grown SiNWs in the 620-950 nm spectral range is a clear indication of the occurrence of quantum confinement. Such a PL emission is in accordance with the TEM results which revealed that the size of nanostructures are indeed below the exciton Bohr radius of silicon
Variations on the Author
Full text link“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
Full text linkWe 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
Full text linkWe 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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