Electronic structure and properties of sputtered Ta-Cu films

Authors

K.D. Aylesworth, University of Nebraska - Lincoln
Sitaram Jaswal, University of NebraskaFollow
M.A. Engelhardt, University of Nebraska - Lincoln
Z.R. Zhao, University of Nebraska - Lincoln
David J. Sellmyer, University of Nebraska-LincolnFollow

Date of this Version

February 1988

Comments

Published by American Physical Society. Phys. Rev. B 37, 2426 (1988). http://prb.aps.org. Copyright © 1988 American Physical Society. Permission to use.

Abstract

Films of Ta_xCu_1-x have been produced in a co-sputtering system with dc- and rf-sputtering guns and a substrate attached to a rapidly rotating, water-cooled table. Samples were produced in the composition range 0.1≤x≤0.9. X-ray diffraction and electrical resistivity data between 4.2 and 300 K have been obtained. Diffraction measurements show that for 0.6≤x≤0.9 the samples are glassy. The room-temperature resistivities follow the Mooij correlation with a zero temperature coefficient of resistivity at a resistivity of 35 μΩ cm. The resistivity-versus-temperature data for Ta_0.90Cu_0.10 are compared to the extended Ziman-Faber theory and a localization theory by Kaveh and Mott. Of these two theories, the Kaveh-Mott theory best describes the experimental results. Ultraviolet and x-ray photoemission measurements have been made as a function of composition. The position of the Cu 3x levels appears to be correlated with the amorphous or crystalline character of the structure. A linear muffin-tin-orbital calculation of the electronic structure of amorphous Ta_0.59Cu_0.41 has been performed. The calculation, based on a periodically extended amorphous cluster of 39 atoms, gave an electronic density of states in good agreement with photoemission results.