1,721,002 research outputs found
Epitaxial growth of Ge2Sb2Te5 thin films on BaF2 substrates at room temperature by pulsed laser deposition
No full textEpitaxial Ge2Sb2Te5 (GST225) thin films, key materials for phase change memory, were successfully grown on the (111) surface of BaF2 single-crystal substrates at room temperature using pulsed laser deposition. Laser fluence and repetition rate played a crucial role in controlling the microstructure of the thin films. Epitaxial growth was achieved at fluences between 2 and 4 J cm−2 with a low repetition rate of 1 Hz. In contrast, a fluence of 1 J cm−2 combined with repetition rates of 1, 10, and 100 Hz, as well as fluences of 2–4 J cm−2 combined with repetition rates of 10 and 100 Hz, resulted in amorphous thin films. The crystalline GST225 layers exhibited a cubic structure with slightly expanded lattice parameters, suggesting a partial relaxation of lattice mismatch. X-ray pole figures and φ-scans revealed a well-aligned out-of-plane orientation, accompanied by rotational twin domains. The out-of-plane epitaxial relationship is determined to be GST225(111)||BaF2(111), whereas the in-plane relationship is characterized by two directions, i.e., GST225[110]||BaF2[110] and GST225[110]||BaF2[1–10]. Atomic-resolution scanning transmission electron microscopy confirmed the cubic phase and uncovered localized planar defects resembling van der Waals-like gaps. Overall, this study demonstrates the feasibility of growing high-quality, epitaxial phase change materials at room temperature, enabling prospects for low-power, high-speed memory devices, and next-generation reconfigurable photonic systems
Impact of disorder on optical reflectivity contrast of epitaxial Ge<sub>2</sub>Sb<sub>2</sub>Te<sub>5</sub> thin films
No full textClassification of the optical reflectivity contrasts of single-phase, epitaxial Ge2Sb2Te5 thin films with respect to the vacancy arrangements.</p
Solid state reactions in electroceramic systems
No full textFestkörperreaktionen in keramischen Materialien sind seit vielen Jahren untersucht, weil sie technologisch bedeutsam und wissenschaftlich interessant sind. Modellexperimente sind sehr gut geeignet um verschiedene Aspekte von komplexeren Festkörperreaktionen zu untersuchen. Bei diesem Ansatz wird an Stelle von polykristallenen Materialien ein Einkristall als Reaktant benutzt. In solchen Modellexperimente können die Bildung und Orientierung der Reaktionsprodukte mit verschiedenen strukturellen Methoden wie Röntgendiffraktometrie (XRD) und Transmissionselektronenmikroskopie (TEM) gut charakterisiert werden. Diese Doktorarbeit befasst sich mit Festkörperreaktionen in Modellexperimenten. In der Doktorarbeit wurden Festkörperreaktionen in verschiedenen oxidische Systemen, nämlich BaCO3-TiO2, BaO-TiO2, SrO-TiO2, CaO-TiO2 and MgO-TiO2, untersucht. Der Radius des Elements, das mit TiO2 reagiert, wurde von 139 pm für BaO (BaCO3) zu 75 pm für MgO variiert. In den ersten zwei Systemen BaCO3-TiO2 und BaO-TiO2 wurden Festkörperreaktionen von festem BaCO3 und BaO-Dampf auf TiO2 Substraten mit verschiedener crystallographischer Struktur (Anatas und Rutil) untersucht. Das Hauptziel dieses Teils der Doktorarbeit war den Mechanismus der Bildung von BaTiO3 im Vakuum und in der Luft zu untersuchen. In den folgenden drei Systemen, SrO-TiO2, CaO-TiO2 and MgO-TiO2, wurden Festkörperreaktionen zwischen TiO2 (Rutil) Einkristallen und SrO-, CaO- oder MgO-Dampf untersucht. Die primären Ziele dieses Teils der Arbeit waren: (1) die Orientierungsbeziehungen zwischen dem Perowskit und TiO2 (Rutil) mit denjenigen für die Perowskite SrTiO3 und CaTiO3, sowie für das rhombohedrische MgTiO3 zu vergleichen; (2) mögliche topotaktische Orientierungsbeziehungen zwischen dem tetragonalen TiO2 (Rutil) und den rhombohedrischen MgTiO3 Phase zu bestimmen; (3) den Einfluss der Kristallographie auf die Bildung der ersten Phase bei topotaktischen Festkörperreaktionen im System MgO-TiO2 zu studieren.Solid state reactions in ceramic materials are investigated since many years under both fundamental and technological points of view. Model experiments are well suited to study various aspects of complex solid state reactions. In this approach, instead of using polycrystalline materials, one reactant is a bulk single crystal. In such model experiments, the formation and orientation of the reaction products can be well characterised by several structural techniques such as X-ray diffractometry (XRD) and transmission electron microscopy (TEM). This Ph.D. work deals with solid state reactions in model experiments. In the work, solid state reactions in different oxide systems, viz. BaCO3-TiO2, BaO-TiO2, SrO-TiO2, CaO-TiO2 and MgO-TiO2, were investigated. The radius of the element reacting with TiO2 was varied from 139 pm for BaO (BaCO3) to 75 pm for MgO. In the first two systems, BaCO3-TiO2 and BaO-TiO2, the solid state reaction of solid BaCO3 and BaO vapour with TiO2 substrates of different crystallographic structure (anatase and rutile) were studied. The main goal of this part of the Ph.D. work was to study the mechanism of BaTiO3 formation in vacuum and in air. In the next three systems, SrO-TiO2, CaO-TiO2 and MgO-TiO2, the solid state reaction between TiO2 (rutile) single crystals and SrO, CaO or MgO vapour was studied. The primary aims of this part of the Ph.D. thesis were: (1) To compare the orientation relationships found for the BaTiO3 perovskite grown on TiO2 (rutile) substrates with those for SrTiO3 and CaTiO3 perovskite as well as for the rhombohedral MgTiO3; (2) To determine possible topotaxial orientation relationships between tetragonal TiO2 (rutile) and the rhombohedral MgTiO3 phase; (3) To study the role of crystallography in topotaxial first phase formation in the MgO-TiO2 system.von Andriy Lotny
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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