1,720,983 research outputs found
Thermal Stability of Sputtered Tungsten Nitrides for Solar Thermal Applications
No full textIn this work, tungsten nitrides sputtered at different powers supplied to a W target (300 W, 500 W, 700 W) and proposed for solar thermal applications as part of solar absorbers, as active and robust materials for capacity energy storage and as plasma-facing materials were annealed in vacuum at medium-high temperatures (470 °C, 580 °C) and characterized by means of X-ray diffraction (XRD), AFM, micro-Raman, FTIR, UV–VIS–-NIR, sheet, surficial energy and wetting angle measurements. From the overall set of analyses, some important modifications and differences between samples after annealing emerged (which will be useful for selecting them for specific applications) and have been correlated to sputtered W metallic clusters’ ability to adsorb, form complexes with and react with the strong N2 triple bond under the various plasma conditions of a reactive sputtering process. In particular, the 300 W film of poor crystalline quality as deposited, after annealing released entrapped nitrogen and retained its W2N structure up to a temperature of 580 °C. Despite there being no phase transition, there was an increase in sheet resistance, which is detrimental because the preservation of metallic character is an important requisite for the proposed applications. The 500 W film had a stable crystalline structure and a metallic character unmodified by increasing temperature. The 700 W film, whose structure as deposited was almost amorphous, underwent the most severe modification after annealing: crystallizing, disproportioning and giving rise to a composite and porous nature (W + WNx) not ideal for spectrally selective coating applications, but useful for tailoring capacitive energy storage devices, or for catalysts for hydrogen evolution reactions (as an alternative to platinum) in alkaline water electrolysis
Space charge limited current and photoconductive effect in few-layer MoS2
No full textWe analyse the conduction mechanism and the electrical photoresponse of chemical-vapor deposited MoS2 few-layers on SiO2/Si substrate. We perform temperature dependent I-V measurements and report a space-charge limited conduction due to the presence of an exponential distribution of trap states in the MoS2 band-gap. We estimate the density of trap states as 1010 – 1011 cm −2 from the temperature-independent critical drain-source voltage. We also investigate the MoS2 photocurrent under white light at different incident powers. We use a modified Hornbeck-Hayens model to study the photoconductive effect and for an alternative estimation of the trap state density
Two-dimensional effects in Fowler-Nordheim field emission from transition metal dichalcogenides
No full textWe report field emission from bilayer MoS 2 and monolayer WSe 2 synthesized by CVD on SiO 2/Si substrate. We show that the emitted current follows a Fowler-Nordheim model modified to account for the two-dimensional confinement of charge carriers. We derive the figures of merit of field emission and demonstrate that few-layer transition-metal dichalcogenides are suitable for field emission applications
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
Field emission from mono and two-dimensional nanostructures
No full textIn recent years, nanostructured materials have been deeply investigated for field emission applications. The exploitation of different geometries and morphologies is a key ingredient for the realization of proficient field emitter devices. In this work, we highlight the features of two differently shaped nanostructured materials such as molybdenum disulphide and gallium oxide. We show that MoS2 nanoflowers and β-Ga2O3 nanopillars can achieve different field emission performance in terms of maximum current density, turn-on field and field enhancement factor
Two-dimensional effects in Fowler-Nordheim field emission from transition metal dichalcogenides
No full textWe report field emission from bilayer MoS 2 and monolayer WSe 2 synthesized by CVD on SiO 2/Si substrate. We show that the emitted current follows a Fowler-Nordheim model modified to account for the two-dimensional confinement of charge carriers. We derive the figures of merit of field emission and demonstrate that few-layer transition-metal dichalcogenides are suitable for field emission applications
Environmental effects on transport properties of PdSe2 field effect transistors
No full textWe study the effect of pressure, voltage sweeping rate and electron irradiation on the transfer characteristics of field effect transistors fabricated by using exfoliated palladium diselenide flake as transistor channel and Ti/Au metallic electrodes as source and drain. The silicon substrate is used as gate, the flake being transferred on Si/SiO2 substrate. We report ambipolar behavior for the devices under investigation and we demonstrate that external stimuli have dramatic effects on the transport properties. In particular, increasing the acquisition time (by using slower sweeping rate) we demonstrate that the hysteresis observed in the transfer characteristics is widened. Electron irradiation, necessary for SEM imaging of the device, also dramatically affects the characteristics due to induced defects and consequent charge trapping at PdSe2 and SiO2. Finally, we demonstrate that the device can be tuned from n-type conduction in vacuum, to p-type conduction in atmospheric pressure
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
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