1,720,969 research outputs found
The Charge Transport Properties of a HWCVD a-Si:H Thin Film under Bending Pressure
No full textThe transient thermoelectric effects (TTEs) method is used to measure the ambipolar space charge built up in a low-pressure hot wire chemical vapor deposition (HWCVD) technique a-Si:H layer deposited on a glass substrate. The stage 2 TTE-transients yield the trap state density difference with and without bending pressure up to 9 bars. The a-Si:H sample shows a reduction of the negative storage peaks at 0.045eV and 0.026eV with increasing pressure, while the positive (hole trap) peak and the zero crossing practically do not change with the pressure. At the maximum bending pressure, the negative peaks are almost zero and shifted into the band gap or toward the conduction band. Our result shows that it is necessary to produce and mount hydrogenated thin film solar cell stress-free
Determination of the trap state density differences in hydrogenated microcrystalline silicon-germanium (Si : Ge : H) alloys
No full textTime resolved photo-and thermoelectric effects (TTE) can be used to simultaneously determine, trap levels and trap state density differences in microcrystalline (muc-SiGe:H) samples. Here, in particular, the trap state density differences are obtained from the decay of the ambipolar charge distribution, i.e. stage II of the TTE transients. This type of spectroscopy has been applied for the first time to p,c-SiGe:H samples and indeed trap states which seem to relate to concentration fluctuations, i.e. Si(Ge) and Ge(Si) clusters are observed. (C) 2004 Elsevier B.V. All rights reserved
The charge transport properties of a-Si : H thin films under hydrostatic pressure
No full textTime resolved thermoelectric effects (TTE) were used to simultaneously determine trap levels and trap state density differences in amorphous (a-Si:H) samples. In particular, the trap state density differences are obtained from the decay of the ambipolar charge distribution, i.e. stage 2 of the TTE transients. The trap state difference density is measured under hydrostatic pressures, up to 2.2 kbar. The trap state density difference changes from a negative peak to a positive peak with increasing hydrostatic pressure, suggesting a significant pressure induced shift of the electron and hole trap levels. (c) 2006 Elsevier B.V. All rights reserved
Determination of the trap state density differences in hydrogenated amorphous silicon-germanium alloys
No full textTime-resolved photo- and thermoelectric effects (TTE) were used to determine simultaneously trap levels and trap state density differences in amorphous (a-SiGe:H) samples. In particular, the trap state density differences are obtained from the decay of the ambipolar charge distribution (i.e., stage II of the TTE transients). This type of spectroscopy has been applied for the first time to a-SiGe:H samples, and indeed trap states that seem to relate to concentration fluctuations, that is, Si(Ge) and Ge(Si) clusters, are observed
Evidence of photogenerated space charges in the charge ordered state of Pr0.63Ca0.37MnO3 single crystals
No full textTime-resolved thermoelectric power measurements on bulk single crystals with composition close to charge ordered compound Pr2/3Ca1/3MnO3 show a voltage transient V-2(t) for T < T-co, which is superimposed to and faster as the quasistatic thermovoltage decay V-3(t) which is usually the only transient observed with manganite ceramic. From V-3(t) we derive the heat conductivity k and thermopower S in the temperature range 90 K < T < 350 K. The extra transient is ascribed to the decay of an ambipolar charge distribution in trap states which appears only in the charged ordered regime of x = 0.37. First data on intrinsic and/or extrinsic trap level distributions are given. (C) 2004 Elsevier B.V. All rights reserved
The baric coefficient of resistance of Mn1.9Cr0.1Sb as measured by the double AC method
No full textThe baric coefficient of resistance of the magnetocaloric cycle working medium Mn1.9Cr0.1Sb, aside from the peak which is expected and related to the pressure shift of the AF-Fr transition temperature T-s(p), shows two sidebands which are probably related to the percolation of phase domains. (c) 2007 Elsevier B.V. All rights reserved
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
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