1,720,967 research outputs found
Peculiarities of current transport in titanium oxide-silicon heterostructures
No full textThe mechanisms of charge carrier injection into Ti-TiO2-(n,p)-Si heterostructures have been studied. The influence of the porous TiO2 structure and the silicon substrate type on the electrical characteristics of heterostructures is analyzed. The charge transfer is shown to be accompanied by the appearance of a compensating polarization charge on the surface of TiO2 nanoparticles. Correlations between the type of adsorbed molecules and the conditions of the current flow have been determined. In Ti-TiO2-p-Si heterostructures, a change of the ratio between the numbers of injected electrons and holes can lead to the negative-conductivity effect. ©2012
Charge transport in Si-SiO2 and Si-TiO2 nanocomposite structures
No full textThe experimental data on dispersed Si-SiO2 and Si-TiO2 nanocomposite structures different in terms of physical, chemical, and insulator properties of oxide components are reported. The parameters of the nanocomposite structures are studied by FTIR spectroscopy and impedance spectroscopy. It is shown that, in such structures, the mechanisms of charge-carrier transport are defined by the properties of Si nanocrystallites and the corresponding oxide as well as by interaction processes at interfaces between grains
Impedance spectroscopy of composites based on porous silicon and silica aerogel for sensor applications
No full textElectrophysical and optical properties of heterogeneous composite systems based on nanosilicon (nc-Si) and silica aerogel (SiOx) powders have been investigated using impedance spectroscopy and FTIR spectroscopy methods. In FTIR transmittance spectra the presence of vibration modes of hydroxyl groups covering the internal surface of SiOx matrix as well as associated Si-OH groups has been revealed that should determine the sensing behavior of considered composites mainly under water treating. Based on impedance measurements possible mechanisms of charge carrier transport have been proposed. It was shown that the main process in carrier transport of pressed SiOx/nc-Si composite structures is the percolation tunneling of charge carriers through the silicon nanoclusters system. The dynamic interaction of composite structures with water molecules and pure ethyl alcohol has been investigated. It was revealed that desorption kinetics of SiOx/nc-Si nanocomposites are characterized by higher desorption rate compared to SiOx samples. The relative change of resistance value under water treating δR/R ≅ 0.99 was almost similar for all investigated samples that confirmed the crucial role of oxide matrix in adsorption-desorption processes of considered composite structures. It was concluded that such sensing behavior could be utilized for construction the chemical sensors of humidity and alcohol based on porous SiOx and SiOx/nc-Si nanocomposites. © 2013-STC "Institute for Single Crystal"
Impact of nanoporous metal oxide morphology on electron transfer processes in Ti-TiO2-Si heterostructures
No full textBy sol-gel synthesis a nanosized porous layers of TiO2 with different porosities and specific surface area were fabricated on silicon substrates. The created Ti-TiO2-(n,p)Si heterostructures were studied by the impedance spectroscopy. The significant influence of structure of porous TiO2 and type of silicon substrate on the dependence of capacity and active conductivity on an applied voltage bias is observed. In the frame of the proposed equivalent circuit model the analysis of the contribution of nanocrystals and intercrystalline boundaries into electron transfer processes is carried out. It is observered the effect of negative differential conductivity that is governed by the changing of the capture of injected electrons and holes in porous-TiO2
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
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