1,720,994 research outputs found
Atomic-Layer-Deposited MoNx Thin Films on Three-Dimensional Ni Foam as Efficient Catalysts for the Electrochemical Hydrogen Evolution Reaction
No full textFuture realization of a hydrogen-based economy requires a high-surface-area, low-cost, and robust electrocatalyst for the hydrogen evolution reaction (HER). In this study, the MoNx thin layer is synthesized on to a high-surface area three-dimensional (3D) nickel foam (NF) substrate using atomic layer deposition (ALD) for HER catalysis. MoNx is grown on NF by the sequential exposure of Mo(CO)(6) and NH3 at 225 degrees C. The thickness of the thin film is controlled by varying the number of ALD cycles to maximize the HER performance of the MoNx/NF composite catalyst. The scanning electron microscopy and transmission electron microscopy (TEM) images of MoNx/NF highlight that ALD facilitates uniform and conformal coating. TEM analysis highlights that the MoNx film is predominantly amorphous with the nanocrystalline MoN grains (4 nm) dispersed throughout it. Moreover, the high-resolution (HR)-TEM analysis shows a rough surface of the MoNx film with an overall composition of Mo0.59N0.41. X-ray photoelectron spectroscopy depth-profile analysis reveals that oxygen contamination is concentrated at the surface because of surface oxidation of the MoN film under ambient conditions. The HER activity of MoNx is evaluated under acidic (0.5 M H2SO4) and alkaline (0.1 M KOH) conditions. In an acidic electrolyte, the sample prepared with 700 ALD cycles exhibits significant HER activity and a low overpotential (eta) of 148 mV at 10 mA cm(-2). Under an alkaline condition, it achieves 10 mA cm(-2) with eta of 125 mV for MoNx/NF (700 cycles). In both electrolytes, the MoNx thin film exhibits enhanced activity and stability because of the uniform and conformal coating on NF. Thus, this study facilitates the development of a large-area 3D freestanding catalyst for efficient electrochemical water-splitting, which may have commercial applicability
A bilayer diffusion barrier of Ru/WSixNy for advanced Cu interconnects
No full textBilayers of Ru (7 nm)/WSixNy (8 nm) prepared by sputtering were investigated as diffusion barriers between Cu and Si for direct-platable Cu interconnects. Four different WSixNy films were prepared by using various N-2/Ar flow rate ratios during sputtering of a WSi2.7 target. Sheet resistance measurements and X-ray diffractometry analysis showed that Ru/WSixNy bilayer diffusion barriers prevented Cu diffusion during 30 min of annealing at temperatures of up to 550-750 degrees C, while the Ru single layer of the same thickness (15 nm) failed after annealing at 400 degrees C by the formation of copper silicide due to the diffusion of Cu into Si. It was shown that the performances of bilayer diffusion barriers were improved as the nitrogen content in the WSixNy films was increased, which can be explained based on the results from transmission electron microscopy and X-ray photoelectron spectroscopy analysis of WSixNy films deposited with different N-2/Ar flow rate ratios. From the results, the Si-N and W-N chemical bonds are strengthened as the N contents in the WSixNy films are increased by increasing the N-2 flow rate during the deposition. The results indicate that the formation of both Si-N and W-N bonds will give an effective diffusion barrier against Cu diffusion. (C) 2012 Elsevier B.V. All rights reserved
Atomic layer deposition of ruthenium (Ru) thin films using ethylbenzen-cyclohexadiene Ru(0) as a seed layer for copper metallization
No full textRuthenium (Ru) thin films were grown on thermally-grown SiO2 substrates using atomic layer deposition (ALD) by a sequential supply of (ethylbenzene)(1,3-cyclohexadiene)Ru(0) (EBCHDRu, C14H18Ru), and molecular oxygen (O-2) at deposition temperatures ranging from 140 to 350 degrees C. A self-limiting film growth was confirmed at the deposition temperature of 225 degrees C and the growth rate was 0.1 nm/cycle on the SiO2 substrate with a negligible number of incubation cycles (approximately 2 cycles). Plan-view transmission electron microscopy analysis showed that nucleation was started after only 3 ALD cycles and the maximum nuclei density of 1.43 x 10(12)/cm(2) was obtained after 5 ALD cycles. A continuous Ru film with a thickness of similar to 4 nm was formed after 40 ALD cycles. The film resistivity was decreased with increasing deposition temperature, which was closely related to its crystallinity, microstructure, and density, and the minimum resistivity of similar to 14 mu Omega-cm was obtained at the deposition temperature of 310 degrees C. The step coverage was approximately 100% at trench (aspect ratio: 4.5) with the top opening size of similar to 25 nm. Finally, the ALD-Ru film was evaluated in terms of its performance as a seed layer for Cu electroplating. (c) 2013 Elsevier B.V. All rights reserved
Characteristics ofMoSe(2) formation during rapid thermal processing ofMo-coated glass
No full textMulti-layered Mo, prepared using an in-line sputtering system, was selenized by reaction with Se vapor and thermal annealing of bilayer Mo/Se samples. In situ high-temperature X-ray diffraction analysis indicated that the phase evolution of the glass/Mo/Se sample during heat treatment was similar to that of the selenization of glass/Mo with Se vapor, except for crystallization of Se in the glass/Mo/Se sample. However, the MoSe2 layer formed from the selenization of the Mo layer by Se vapor preferentially grew perpendicularly to the Mo surface, whereas MoSe2 formed from the reaction of Mo with Se liquid showed random orientation. The detailed reaction pathways of the double-layer random-MoSe2/vertical-MoSe2 formation from the Mo/Se bilayer sample were suggested on the basis of the several characterization results including X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, energy dispersive X-ray spectroscopy and selected-area electron diffraction patterns. © 2012 Elsevier B.V.1
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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