1,721,037 research outputs found
Numerical simulation of self-organized nano-islands in plasma-based assembly of quantum dot arrays
No full textThis work presents the details of the numerical model used in simulation of self-organization of nano-islands on solid surfaces in plasma-assisted assembly of quantum dot structures. The model includes the near-substrate non-neutral layer (plasma sheath) and a nanostructured solid deposition surface and accounts for the incoming flux of and energy of ions from the plasma, surface temperature-controlled adatom migration about the surface, adatom collisions with other adatoms and nano-islands, adatom inflow to the growing nano-islands from the plasma and from the two-dimensional vapour on the surface, and particle evaporation to the ambient space and the two-dimensional vapour. The differences in surface concentrations of adatoms in different areas within the quantum dot pattern significantly affect the self-organization of the nano-islands. The model allows one to formulate the conditions when certain islands grow, and certain ones shrink or even dissolve and relate them to the process control parameters. Surface coverage by selforganized quantum dots obtained from numerical simulation appears to be in reasonable agreement with the available experimental results
Self-organized nanoarrays : plasma-related controls
No full textThe paper presents an investigation of self-organizational and -assembly processes of nanostructure growth on surfaces exposed to low-temperature plasmas. We have considered three main growth stages-initial, or sub-monolayer growth stage, separate nanostructure growth stage, and array growth stages with the characteristic sizes of several nm, several tens of nm, and several hundreds of nm, respectively, and have demonstrated, by the experimental data and hybrid multiscale numerical simulations, that the plasma parameters can strongly influence the surface processes and hence the kinetics of self-organization and -assembly. Our results show that plasma-controlled self-organization is a promising way to assemble large regular arrays of nanostructures. © 2008 IUPAC
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
Templated i-PVD of metallic nanodot arrays
No full textThe results of numerical simulation of plasma-based, porous, template-assisted nanofabrication of Au nanodot arrays on highly-doped silicon taking into account typical electron density of low-temperature plasma of 1017-1018 m-3 and electron temperature of 2-5 eV are reported here. Three-dimensional microscopic topography of ion flux distribution over the outer and inner surfaces of the nanoporous template is obtained via numerical simulation of Au ion trajectories in the plasma sheath, in the close proximity of, and inside the nanopores. It is shown that, by manipulating the electron temperature, the cross-sheath potential drop, and by additionally altering the structure of the nanoporous template, one can control the ion fluxes within the nanopores, and eventually maximize the ion deposition onto the top surface of the developing crystalline Au nanodots (see top panel in the figure). In the same time, this procedure allows one to minimize amorphous deposits on the sidewalls that clutter and may eventually close the nanopores, thus disrupting the nanodot growth process, as it is shown in the bottom panel in the figure on the right
Ge/Si Quantum Dot Formation From Non-Uniform Cluster Fluxes
Full text linkThe controlled growth of ultra-small Ge/Si quantum dot (QD) nuclei (≈1 nm) suitable for the synthesis of uniform nanopatterns with high surface coverage, is simulated using atom-only and size non-uniform cluster fluxes. It is found that seed nuclei of more uniform sizes are formed when clusters of non-uniform size are deposited. This counter-intuitive result is explained via adatom-nanocluster interactions on Si(100) surfaces. Our results are supported by experimental data on the geometric characteristics of QD patterns synthesized by nanocluster deposition. This is followed by a description of the role of plasmas as non-uniform cluster sources and the impact on surface dynamics. The technique challenges conventional growth modes and is promising for deterministic synthesis of nanodot arrays.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/56174/1/638_ftp.pd
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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