1,720,956 research outputs found
Reversible and irreversible effects after oxygen exposure in thick (>1 μm) silicon films deposited by VHF-PECVD on glass substrates investigated by dual beam photoconductivity
No full textMetastability and instability effects due to oxygen exposure in thick intrinsic hydrogenated microcrystalline silicon films deposited by very high frequency plasma enhanced chemical vapour deposition on smooth glass substrates were investigated using temperature-dependent dark conductivity, steady state photoconductivity, and sub-bandgap absorption measurements obtained using the dual beam photoconductivity (DBP) method. No significant changes in dark conductivity and photoconductivity were detected even after long-term air exposure of samples in room ambient as well as after oxygen exposure when samples were characterized in oxygen ambient. However, characterization of the oxygen-exposed state in high vacuum caused an increase in dark conductivity and photoconductivity as well as a significant decrease in the sub-bandgap absorption coefficient spectra in the low energy region in samples with . These changes are partially irreversible for samples and mostly reversible for compact materials with significant amorphous fraction. No detectable metastable changes occurred in microcrystalline silicon samples with as well as in pure amorphous silicon
Investigation of metastability and instability effects on the minority carrier transport properties of microcrystalline silicon thin films by using the steady-state photocarrier grating technique
No full textMetastability effects in hydrogenated microcrystalline silicon thin films due to air, high purity nitrogen, helium, argon, and oxygen were investigated using temperature-dependent dark conductivity, photoconductivity, and steady-state photocarrier grating methods. It was found that short-term air, nitrogen, and inert gases caused a small reversible increase of σDark and σphoto within a factor of two, but they did not affect the minority carrier μτ-products significantly. These changes are partially reduced by vacuum treatment and completely reduced after heat treatment at 430 K. However, oxygen gas treatment at 80 °C resulted in more than an order of magnitude increase in both σDark and σphoto and an increase in the diffusion length, LD, by 50% from that of the annealed-state value in highly crystalline samples, while no significant metastability is detected in amorphous and low crystalline silicon thin films. A following heat treatment partially recovers both σDark and σphoto to their annealed-state values, while LD decreases only slightly. Such increase in the LD values could be due to a decrease in the density of recombination centers for holes below the Fermi level, which may be related to passivation of defects by oxygen on the surface of crystalline grains
Investigation of meta- and in-stability effects in hydrogenated microcrystalline silicon thin films by the steady-state measurement methods
No full textMetastability effects because of atmospheric exposure, high purity gasses, and deionized water in hydrogenated microcrystalline silicon thin films with different crystalline volume fractions were studied using well accepted steady-state characterization methods of dark conductivity, steady-state photoconductivity, steady-state photocarrier grating (SSPG) and dual beam photoconductivity (DBP) methods. A standard measurement procedure has been established before using the steady state methods, in which a steady state condition of dark conductivity was established by monitoring the time dependence of dark conductivity. Samples deposited on smooth glass and rough glass substrates exhibit similar reversible and irreversible changes in the properties of microcrystalline silicon film. A reliable correlation of reversible and irreversible changes indicate that dark conductivity and photoconductivity values increase, sub-bandgap absorption spectrum obtained from DBP method decrease and correspondingly minority carrier diffusion lengths obtained from the SSPG method increase in the metastable state in various amount for microcrystalline films with crystalline volume fraction, > 0.30. Amorphous silicon and microcrystalline silicon films with < 0.30 do not show detectable metastable changes as samples exposed to atmospheric condition as well as high purity oxygen gas and deionized water
Metastability effects in hydrogenated microcrystalline silicon thin films investigated by the dual beam photoconductivity method
No full text24th International Conference on Amorphous and Nanocrystalline Semiconductors (ICANS) - AUG 21-26, 2011 - Nara, JAPANGunes, Mehmet/0000-0001-9094-6059; Yilmaz, Gokhan/0000-0003-0834-9736; Smirnov, Vladimir/0000-0002-2215-206X; Finger, Friedhelm/0000-0002-6250-7240; cansever, hamza/0000-0003-0595-4949WOS: 000310394700035Metastability effects in microcrystalline silicon (mu c-Si:H) thin films have been investigated using dark conductivity, sigma(D), photoconductivity, sigma(ph), and sub-bandgap absorption methods. Nitrogen and inert gasses can cause reversible aging effect in conductivities but not in the sub-bandgap absorption. However. DI water and O-2 gas treatment result in both reversible and nonreversible effects in conductivities as well as in the sub-bandgap absorption. Only oxygen affected the dark conductivity reversibly in amorphous silicon, a-Si:H, films, other results were unaffected from the aging and annealing processes applied. (C) 2012 Elsevier B.V. All rights reserved.Japan Soc Promot Sci, 147th Comm Amorphous & Nanocrystalline Mat, Commemorat Org Japan World Exposit, Osaka Univ Global COE Program Core Res & Engn Adv Mat Interdisciplinary Educ Ctr Mat Sci, Asahi Glass Fdn, ALS Tech Co Ltd, Crev Inc, Coherent Inc, DAIHEN Corp, Dainippon Screen Co Ltd, HOYA Corp, J A Woollam Co Inc, Kaneka Corp, KEYENCE Corp, Mitsubishi Heavy Industries Ltd, Nano Photon, Nisshin Steel Co Ltd, Samco Inc, Sanyo Elect Co Ltd, Semicond Energy Lab Co Ltd, Shimadzu Corp, SNK Corp, Tokyo Elect Ltd, TOYO Corp, ULVAC In
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
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