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Title: WC/a-C nanocomposite thin films: Optical and electrical properties

Abstract

WC/amorphous carbon (a-C) thin films were deposited by dual magnetron sputtering from individual WC and graphite targets. The influence of film composition and microstructure on the optical and electrical properties was investigated. As evidenced by x-ray photoelectron spectroscopy and grazing angle x-ray diffraction measurements, the WC/a-C films are composite materials made of hexagonal W{sub 2}C and/or cubic {beta}-WC{sub 1-X} nanocrystallites embedded in (a-C) matrix. The optical properties were studied by spectroscopic ellipsometry and the electrical resistivity was measured by the van der Pauw method between 20 and 300 K. Both the optical and the electrical properties of the WC/a-C films are correlated with the chemical composition and microstructure evolution caused by a-C addition. The optical properties of W{sub 2}C/a-C and {beta}-WC{sub 1-x}/a-C films with a-C content {<=}10 at. % are explained by modeling their dielectric functions by a set of Drude-Lorentz oscillators. Further increase in a-C content leads only to the formation of {beta}-WC{sub 1-x}/a-C nanocomposite structures and their optical properties progressively evolve to those of a-C single phase. The electrical resistivity as a function of the temperature of all the films exhibits a negative temperature coefficient of resistivity. Theoretical fitting using the grain-boundary scattering model shows that the transportmore » properties are mainly limited by the grain size and electron mean free path parameters.« less

Authors:
;  [1]; ;  [2]
  1. Instituto de Ciencia de Materiales de Sevilla, CSIC-US, Sevilla 41092 (Spain)
  2. Ecole Polytechnique Federale de Lausanne, IPMC-SB, CH-1015 Lausanne (Switzerland)
Publication Date:
OSTI Identifier:
21186008
Resource Type:
Journal Article
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 105; Journal Issue: 3; Other Information: DOI: 10.1063/1.3060717; (c) 2009 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-8979
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CHEMICAL COMPOSITION; COMPOSITE MATERIALS; CRYSTAL STRUCTURE; ELECTRIC CONDUCTIVITY; ELLIPSOMETRY; GRAIN BOUNDARIES; GRAPHITE; MEAN FREE PATH; NANOSTRUCTURES; OPTICAL PROPERTIES; SPUTTERING; TEMPERATURE COEFFICIENT; TEMPERATURE DEPENDENCE; TEMPERATURE RANGE 0013-0065 K; TEMPERATURE RANGE 0065-0273 K; TEMPERATURE RANGE 0273-0400 K; THIN FILMS; TUNGSTEN CARBIDES; X-RAY DIFFRACTION; X-RAY PHOTOELECTRON SPECTROSCOPY

Citation Formats

Abad, M D, Sanchez-Lopez, J C, Cusnir, N, and Sanjines, R. WC/a-C nanocomposite thin films: Optical and electrical properties. United States: N. p., 2009. Web. doi:10.1063/1.3060717.
Abad, M D, Sanchez-Lopez, J C, Cusnir, N, & Sanjines, R. WC/a-C nanocomposite thin films: Optical and electrical properties. United States. https://doi.org/10.1063/1.3060717
Abad, M D, Sanchez-Lopez, J C, Cusnir, N, and Sanjines, R. 2009. "WC/a-C nanocomposite thin films: Optical and electrical properties". United States. https://doi.org/10.1063/1.3060717.
@article{osti_21186008,
title = {WC/a-C nanocomposite thin films: Optical and electrical properties},
author = {Abad, M D and Sanchez-Lopez, J C and Cusnir, N and Sanjines, R},
abstractNote = {WC/amorphous carbon (a-C) thin films were deposited by dual magnetron sputtering from individual WC and graphite targets. The influence of film composition and microstructure on the optical and electrical properties was investigated. As evidenced by x-ray photoelectron spectroscopy and grazing angle x-ray diffraction measurements, the WC/a-C films are composite materials made of hexagonal W{sub 2}C and/or cubic {beta}-WC{sub 1-X} nanocrystallites embedded in (a-C) matrix. The optical properties were studied by spectroscopic ellipsometry and the electrical resistivity was measured by the van der Pauw method between 20 and 300 K. Both the optical and the electrical properties of the WC/a-C films are correlated with the chemical composition and microstructure evolution caused by a-C addition. The optical properties of W{sub 2}C/a-C and {beta}-WC{sub 1-x}/a-C films with a-C content {<=}10 at. % are explained by modeling their dielectric functions by a set of Drude-Lorentz oscillators. Further increase in a-C content leads only to the formation of {beta}-WC{sub 1-x}/a-C nanocomposite structures and their optical properties progressively evolve to those of a-C single phase. The electrical resistivity as a function of the temperature of all the films exhibits a negative temperature coefficient of resistivity. Theoretical fitting using the grain-boundary scattering model shows that the transport properties are mainly limited by the grain size and electron mean free path parameters.},
doi = {10.1063/1.3060717},
url = {https://www.osti.gov/biblio/21186008}, journal = {Journal of Applied Physics},
issn = {0021-8979},
number = 3,
volume = 105,
place = {United States},
year = {Sun Feb 01 00:00:00 EST 2009},
month = {Sun Feb 01 00:00:00 EST 2009}
}