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Open AccessArticle

Influence of Thickness and Sputtering Pressure on Electrical Resistivity and Elastic Wave Propagation in Oriented Columnar Tungsten Thin Films

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Institut FEMTO-ST, UMR 6174, CNRS, ENSMM, Univ. Bourgogne Franche-Comté, 15B, Avenue des Montboucons, 25030 BESANCON CEDEX, France
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Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 6303, CNRS, Univ. Bourgogne Franche-Comté, 9, Avenue Alain Savary, BP 47 870, F-21078 DIJON CEDEX, France
*
Author to whom correspondence should be addressed.
Nanomaterials 2020, 10(1), 81; https://doi.org/10.3390/nano10010081
Received: 9 December 2019 / Revised: 23 December 2019 / Accepted: 25 December 2019 / Published: 1 January 2020
Tungsten films were prepared by DC magnetron sputtering using glancing angle deposition with a constant deposition angle α = 80°. A first series of films was obtained at a constant pressure of 4.0 × 10−3 mbar with the films’ thickness increasing from 50 to 1000 nm. A second series was produced with a constant thickness of 400 nm, whereas the pressure was gradually changed from 2.5 × 10−3 to 15 × 10−3 mbar. The A15 β phase exhibiting a poor crystallinity was favored at high pressure and for the thinner films, whereas the bcc α phase prevailed at low pressure and for the thicker ones. The tilt angle of the columnar microstructure and fanning of their cross-section were tuned as a function of the pressure and film thickness. Electrical resistivity and surface elastic wave velocity exhibited the highest anisotropic behaviors for the thickest films and the lowest pressure. These asymmetric electrical and elastic properties were directly connected to the anisotropic structural characteristics of tungsten films. They became particularly significant for thicknesses higher than 450 nm and when sputtered particles were mainly ballistic (low pressures). Electronic transport properties, as well as elastic wave propagation, are discussed considering the porous architecture changes vs. film thickness and pressure.
Keywords: sputtering; GLAD; tilted columns; anisotropy; electrical resistivity; elastic wave propagation sputtering; GLAD; tilted columns; anisotropy; electrical resistivity; elastic wave propagation
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MDPI and ACS Style

Chargui, A.; Beainou, R.E.; Mosset, A.; Euphrasie, S.; Potin, V.; Vairac, P.; Martin, N. Influence of Thickness and Sputtering Pressure on Electrical Resistivity and Elastic Wave Propagation in Oriented Columnar Tungsten Thin Films. Nanomaterials 2020, 10, 81.

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