Effective elastic constants of thin-film tungsten-silicide from surface acoustic wave analysis

The dispersion of surface acoustic waves propagating on single-crystal (100) silicon substrates covered by thin films of tungsten-silicide has been investigated using an acoustic material signature technique at a frequency of 339 MHz. The tungsten-silicide layers (500–2500 Å) were deposited using a co-sputtering technique, isochronally annealed at temperatures of 700 and 850 °C for 45 min in an argon atmosphere and examined using Rutherford backscattering spectrometry. Dispersion curves were calculated using a Tiersten model [J. Appl. Phys. 40, 2 (1969)] and fitted to the experimental dispersion data. The effective elastic constants for annealed and ‘‘as-deposited’’ layers were determined as best-fit parameters.