ELASTIC CONSTANTS OF SPUTTERED ZNO FILMS.

The elastic constants of ZnO films deposited by RF magnetron sputtering on Al//2O//3 and Si substrates have been determined through an ultrasonic technique. The experimental procedure followed relies on measurement of the phase velocity of a spectrum of acoustic modes propagating along the layered structure. The effective elastic constants of the film are those which minimize the standard deviation of the exerimental values of the phase velocities from the theoretical ones. Measurements were performed on films of different thickness in the range of 3-17 mu m, deposited on both Z-cut Al//2O//3 and (001)-cut Si substrates. The values obtained for the elastic constants are appreciably lower than those of the bulk material and depend slightly on the film thickness and on the substrate.