1,721,020 research outputs found
Impact of Processing Conditions on the Level Scheme of Silicon Nanowires Synthesized by Top-Down Techniques
No full textMassive and reliable synthesis of semiconductor NWs is an essential pre-requisite for the stepping out from the proof-of-concept stage towards real-world manufacturing of NW-based devices. In this respect it becomes of main concern to answer the question of how growth conditions could introduce point and/or extended defects into NW inner structures, mirroring themselves into the NW level schemes, and finally affecting NW-based device performances.
We report here on the investigation of electrically active defects of Si NWs fabricated by two different top-down techniques, Reactive Ion Etching (RIE) [1] (Fig. 1a) and Metal-Assisted wet Chemical Etching (MaCE) [2] (Fig1b), by means of Deep Level Transient Spectroscopy (DLTS). Our studies reveal the existence of intra-gap levels induced during the Si NWs growth in both cases. We discuss their origin in cross-reference with the different physical mechanisms underlying the samples’ processing features.
Differently from the case of MaCE Si NWs, the low density of RIE etched Si NWs has led us to develop a procedure in order to realize the Schottky barrier junction which is the conditio-sine-qua-non for performing DLTS characterization. Since the same procedure can be adopted for DLTS-probing of NW arrays under every density condition, this in turn opens the way to the systematic study of electrically active defects in semiconductor NWs by means of the sophisticated DLTS technique, of far-reaching consequence about defect characterization in semiconductor NWs.
[1] S. Leopold et al., J. Vac. Sci. Technol. B, 29, 011002 (2011).
[2] A. Irrera et al., Nanotechnology, 23, 075204 (2012)
Properties of Si nanowires as a function of their growth conditions
No full textSilicon nanowires physical properties strongly depend on their growth conditions, as already assessed.
We report on the electrical properties of nanowires (NWs) grown by the vapor–liquid–solid (VLS)
mechanism, one of the most established for NW growth, and by the more recent metal-assisted wet
chemical etching (MaCE).Wet etching growth process promises to be an industrial advantageous way for
growing Si NWs, because of its cheapness, fastness, relative easiness. The electronic level scheme in VLS
grown, boron (B)- and phosphorus (P)-doped NWs has been experimentally investigated. We have
demonstrated that the doping impurities induce the same shallow levels as in bulk silicon. The presence
of two donor levels in the lower half-bandgap is also revealed, which has been successfully related to VLS
growth details.
We report, also, on the first results on the physical properties of Si NW arrays grown by MaCE, and
compare them to those of VLS grown Si NWs
Defect level characterization of silicon nanowire arrays: Towards novel experimental paradigms
No full textThe huge amount of knowledge, and infrastructures, brought by silicon (Si) technology, make Si Nanowires (NWs) an ideal choice for nano-electronic Si-based devices. This, in turn, challenges the scientific research to adapt the technical and theoretical paradigms, at the base of established experimental techniques, in order to probe the properties of these systems. Metal-assisted wet-Chemical Etching (MaCE) [1, 2] is a promising fast, easy and cheap method to grow high aspect-ratio aligned Si NWs. Further, contrary to other fabrication methods, this method avoids the possible detrimental effects related to Au diffusion into NWs. We investigated the bandgap level diagram of MaCE Si NW arrays, phosphorous-doped, by means of Deep Level Transient Spectroscopy. The presence of both shallow and deep levels has been detected. The results have been examined in the light of the specificity of the MaCE growth. The study of the electronic levels in Si NWs is, of course, of capital importance in view of the integration of Si NW arrays as active layers in actual devices
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
Si Nanowires for the Matrix-Free Analysis of Small Molecules: Synthesis, Characterization, and Laser Desorption Ionization Mass Spectrometry Applications
No full textVariations 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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