1,721,039 research outputs found
3D real-space quantum transport simulation of nanowire MOS transistors: Influence of the ionized doping impurity
No full textWe report a numerical study of both donor- and acceptor doping impurity effects in the quantum transport of silicon nanowire metal-oxide-semiconcluctor (MOS) transistors. The code is based on a full three-dimensional (3D) real-space non-equilibrium green function (NEGF) formalism self-consistently coupled with the 3D Poisson equation. The general results show that the influence of an impurity strongly depends on its type. Indeed, an acceptor or a donor will create a repulsive or attractive potential, giving rise to tunneling effect or resonances, respectively. Our calculations analyze the impact on electron density, transmission coefficient and drain current (I(D)) which undergoes variations up to 50%. This pinpoints the importance of intrinsic fluctuations due to doping in ultimate nano-transistors whose magnitude cannot be neglected in the next generations of integrated circuits. (C) 2008 Elsevier Ltd. All rights reserved
Physically based diagonal treatment of the self-energy of polar optical phonons. Performance assessment of III-V double-gate transistors
No full textWe propose a diagonal approximation for the self-energy that describes the interaction between electrons and polar optical phonons in the framework of nonequilibrium Green's function transport simulations. Our model is based on the definition of a scaling factor, which renormalizes the local electron-phonon coupling, to take into account the nonlocality of the interaction and provide the correct scattering rates. While previous studies relied on empirical values of this factor, we derive, from basic physical relationships, analytical expressions in the presence of the one- and two-dimensional confinement of phonons. We apply our model to the self-consistent simulation of double-gate p-type transistors made of technologically relevant III-V materials (InAs, InSb, and GaSb). Their performance is benchmarked, for different crystallographic orientations and strain constraints, against the corresponding Si and Ge devices. We find that the electron-polar optical phonon scattering plays a major role in degrading the performance of the III-V devices and typically results in a widening of the performance gap existing between III-V and Si or Ge devices in ballistic transport condition
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
The optical absorption of the neutral vacancy in diamond
No full textOptical absorption by the neutral vacancy in diamond has been predicted to occur between the ground 1E state and the 1T2 excited state. Both these states are orbitally degenerate and should show Jahn Teller distortions. We have calculated the Huang-Rhys Factor for the transition (the fraction of the intensity in the zero phonon line) and the first and second moments of the absorption band. Also we discuss the response of the zero phonon line to externally applied stresses. Our model assumes that the vacancy interacts with just six modes, corresponding to the normal modes of the neighbours of the vacancy. The coupling of the electronic and nuclear motion is estimated from an LCAO model.
The results are compared with observations of the GR1 band, which has been attributed to the vacancy. The predicted Huang-Rhys factor S ~ 3.7 and the first and second moments of the band support this identification. Further our model predicts that luminescence from this band should be unpolarised, as observed. However the predicted stress splitting of the zero phonon line differs from that observed. Possible explanations of this are discussed
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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