1,720,985 research outputs found
Towards smooth (010) β-Ga2O3 films homoepitaxially grown by plasma assisted molecular beam epitaxy: the impact of substrate offcut and metal-to-oxygen flux ratio
Full text linkSmooth interfaces and surfaces are beneficial for most (opto)electronic devices that are based on thin films and their heterostructures. For example, smoother interfaces in (010) β-Ga2O3/(AlxGa1-x)2O3 heterostructures, whose roughness is ruled by that of the β-Ga2O3 layer, can enable higher mobility 2-dimensional electron gases by reducing interface roughness scattering. To this end we experimentally prove that a substrate offcut along the [001] direction allows to obtain smooth β-Ga2O3 layers in (010)-homoepitaxy under metal-rich deposition conditions. Applying In-mediated metal-exchange catalysis (MEXCAT) in molecular beam epitaxy at high substrate temperatures (Tg = 900 °C) we compare the morphology of layers grown on (010)-oriented substrates having different unintentional offcuts. The layer roughness is generally ruled by (i) the presence of (110)- and -facets visible as elongated features along the [001] direction (rms < 0.5 nm), and (ii) the presence of trenches (5–10 nm deep) orthogonal to [001]. We show that an unintentional substrate offcut of only ≈ 0.1° almost oriented along the [001] direction suppresses these trenches resulting in a smooth morphology with a roughness exclusively determined by the facets, i.e. rms ≈ 0.2 nm. Since we found the facet-and-trench morphology in layer grown by MBE with and without MEXCAT, we propose that the general growth mechanism for (010)-homoepitaxy is ruled by island growth whose coalescence results in the formation of the trenches. The presence of a substrate offcut in the [00-1] direction can allow for step-flow growth or island nucleation at the step edges, which prevents the formation of trenches. Moreover, we give experimental evidence for a decreasing surface diffusion length or increasing nucleation density on the substrate surface with decreasing metal-to-oxygen flux ratio. Based on our experimental results we can rule-out step bunching as cause of the trench formation as well as a surfactant-effect of indium during MEXCAT
Ga2O3 polymorphs: Tailoring the epitaxial growth conditions
Full text linkGallium oxide is a wide bandgap n-type semiconductor highly interesting for optoelectronic applications (e.g., power electronics and solar blind UV photodetectors). Besides its most thermodynamically stable monoclinic β phase, Ga2O3 can crystallize in different polymorphs; among them the corundum α and the orthorhombic ε phases are the most promising ones. In this review we focus on the main aspects that promote the nucleation and stable growth of these Ga2O3 polymorphs. Particular emphasis is given to the ε phase since it is recently gaining increasing attention in the scientific community because of: (i) its higher lattice symmetry with respect to β-Ga2O3, which could favour the realization of heterostructures, (ii) the possibility to be grown on cheap sapphire substrates and (iii) its peculiar piezoelectric properties. While the growth of β-Ga2O3 is widely studied and understood, a thorough and comprehensive analysis of the chemical and physical aspects that allow for the stabilization of the metastable Ga2O3 phases with different synthesis methods is still missing. Therefore, the present review aims at filling this gap, by analysing the relevant growth parameters for several growth techniques (MOVPE, HVPE, mist-CVD, MBE, and PLD), highlighting similarities and differences, looking for a unified framework to understand the growth and nucleation of different Ga2O3 polymorphs. As a conclusion, we highlight practical guidelines for the deposition of the different Ga2O3 polymorphs with all the discussed thin film growth techniques
Rapport V.10. Les bases de plein air et de loisirs de la région parisienne : schéma directeur et méthodologie
No full textThe basic principles in the master plan for the Paris area are outlined, with the names of sites earmarked for priority development for leisure use. Arrangements required to implement these projects include the appointment of a project authority, land purchase, and technical and management studies. The features of sites now under development at Moisson-Sandracourt, Verneuil, Saint-Quentin lake and Viry-Grigny and Créteil park are described and a few details are given on sites at Mantes and Cergy.Principes de base du Schéma Directeur de la Région Parisienne. Sites retenus en priorité pour les aménagements de loisirs. Dispositions prises pour assurer la réalisation des Bases de plein air et de loisirs : choix du maître d’œuvre, acquisitions foncières, études techniques et de gestion. Caractéristiques des diverses bases en cours de réalisation : Moisson-Sandrancourt, Verneuil, lac de Saint-Quentin, parc de Viry-Grigny, parc de Créteil : quelques détails sur les bases de Mantes et de Cergy.Maurel A., Mazzolini P. Rapport V.10. Les bases de plein air et de loisirs de la région parisienne : schéma directeur et méthodologie. In: Utilisation des ressources en eau d'un bassin dans le cadre de l'aménagement du territoire. Compte-rendu des onzièmes journées de l'hydraulique; Paris, 22-24 septembre 1970. Tome 2, 1971
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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