1,721,105 research outputs found
The significance and challenges of direct growth of graphene on semiconductor surfaces
No full textIn the past decade, fundamental graphene research has indicated several excellent electronic properties for graphene such as ultrahigh carrier mobility (~200,000 cm<sup>2</sup> / Vs), micrometer - scale mean free path, electron - hole symmetry and quantum Hall effect [ 1 - 6 ] . Such extraordinary properties , unmatched by any other conventional thin film material, make it an extremely promising material for next generation nano - integrated devices. Despite of this, several fundamental challenges still lay ahead before the introduction of graphene in nanodevices can be envisaged. One major challenge is the ability to confirm the outstanding reported properties for graphene grown over large - area s , on to appropriate substrates . \ud
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Since graphene was isolated first time in 2004 [ 7 ] , several techniques have been demonstrated to produce high quality graphene. The most common techniques are micromechanical exfoliation of single crystal graphite [ 7 ] , chemical vapor deposition (CVD) growth on transition metals and dielectric insulators [ 8 - 10 ] , chemical reduction of graphite oxide (GO) [ 11 ] , carbon nanotubes (CNTs) unzipping [ 12 ] , and high temperature thermal decomposition of silicon carbide (SiC) [ 13 ] . Among these methods, the highest performance graphene devices have been fabricated using mechanically exfoliated flakes. Carrier mobility in excess of ~200,000 cm<sup>2</sup> / V s has been reported for suspended single layer exfoliated graphene at room temperature [ 6 , 14 ] . CVD growth is widely used to produce large - area (up to 30 inch) , high quality graphene on transition metal substrates [ 8 , 15 ] . However, the graphene layers produced in the ways described above need invariably to be transfer red onto a semiconducting or insulating subs trate for device fabrication. Unfortunately, for several compelling reasons, this transfer approach is not compatible with the commercial fabrication of actual nanodevices. First, the transfer of flakes tends to affect the quality of the graphene layer in terms of contamination and formation of detrimental folds and ripples, which can ultimately degrade the performance of the electronic devices [ 16 , 17 ] ..
Diffusion and kinetics in epitaxial graphene growth on SiC
No full textOne of the problems that graphene is facing in electronic applications is its quality, which is still far from the level required to obtain an industrial scale production of reliable nanoscale devices, and it is ultimately related to the growth method. Understanding the kinetics of the graphene growth is an outstanding problem in physics, whose solution is the key to achieve full control on the graphene properties . This chapter deals with the microscopic phenomena occurring during epitaxial graphene growth on SiC by high temperature annealing. We discuss recent experimental and theoretical findings on the Si diffusion in the SiC matrix and on the kinetics of graphene growth as a function of temperature and of time. The theoretical framework developed in this chapter will help to understand the physical basis of the graphene formation, which is essential for a perfect control of the graphene quality, helping to define the optimal conditions for the growth of a continuous monolayer or bilayer graphene on SiC
Electrical leakage phenomenon in heteroepitaxial cubic silicon carbide on silicon
Full text linkHeteroepitaxial 3C-SiC films on silicon substrates are of technological interest as enablers to integrate the excellent electrical, electronic, mechanical, thermal, and epitaxial properties of bulk silicon carbide into well-established silicon technologies. One critical bottleneck of this integration is the establishment of a stable and reliable electronic junction at the heteroepitaxial interface of the n-type SiC with the silicon substrate. We have thus investigated in detail the electrical and transport properties of heteroepitaxial cubic silicon carbide films grown via different methods on low-doped and high-resistivity silicon substrates by using van der Pauw Hall and transfer length measurements as test vehicles. We have found that Si and C intermixing upon or after growth, particularly by the diffusion of carbon into the silicon matrix, creates extensive interstitial carbon traps and hampers the formation of a stable rectifying or insulating junction at the SiC/Si interface. Although a reliable p-n junction may not be realistic in the SiC/Si system, we can achieve, from a point of view of the electrical isolation of in-plane SiC structures, leakage suppression through the substrate by using a high-resistivity silicon substrate coupled with deep recess etching in between the SiC structures
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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