1,720,954 research outputs found
Characterisation of morphology and defects in silicon-germanium virtual substrates
No full textSilicon-germanium heterostructures incorporating virtual substrates are successfully used for both microelectronic and optoelectronic applications. However, their use is limited by their surface morphology (e.g. roughness) and defect (e.g. threading dislocations) density. High quality silicon-germanium heterostructures incorporating virtual substrates have been grown epitaxially using different methods. This study reports the effects of the growth parameters on the morphology and defects in different silicon-germanium heterostructures incorporating virtual substrates grown in the Southampton University Microelectronics center (SUMC) by low pressure chemical vapor deposition (LPCVD). Two types of structures: one with a linear and the other with a step variation of the germanium concentration in the virtual substrate, were grown and characterized. Results obtained were in good agreement with others already reported in the literature for similar structures grown using different epitaxial techniques
Raman study of the strain and H2 preconditioning effect on self-assembled Ge island on Si (001)
No full textAn investigation of the microscopic mechanisms of Ge self-assembling island growth is of great importance for future optoelectronic applications of quantum dot nanostructures. In this study, two sets of self-assembled germanium islands on Si (001) substrate, with and without preconditioning using a high-temperature hydrogenation step on their nucleation and subsequent temporal evolution, were grown by low-pressure chemical vapor deposition (LPCVD). The average germanium concentration, mean diameter of Ge crystalline regions and the strain inside the germanium quantum dots are characterized with high resolution micro-Raman spectroscopy (?RS). Both the intensity and peak position of the Si–Si vibration mode at about 520.07 cm?1 in the Raman spectra have been used as a reference to separate the germanium Raman signal from the overlapping localized Si–Si optical phonon at ?300 cm?1. In the absence of preconditioning, both the island size and germanium composition increase steadily as a function of deposition time. However, on the H2 preconditioned surface, the nucleation and growth rates are greatly increased during the first stages and slow down significantly after deposition for 10 s. Our results indicate that the compressive strain inside the islands acts as a barrier for Ge adatoms to diffuse from the wetting layer into the islands. For the growth times used in this study, for both sets of samples with and without H2 preconditioning, the normalized rate of increase of the Ge concentration (%? [Ge]/? t) decreases by ?0.13/s for a 1% compressive strain increase. The H2 preconditioning can initially increase the density of island nucleation sites, but cannot accelerate the Ge island growth. It tends to lower %? [Ge]/? t by 0.015/s instead. The decreased strain due to surface roughing is the principal reason why the Ge islands grow so rapidly at the beginning on the H2 preconditioned samples
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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