NONLINEAR ELECTROELASTIC EFFECT IN ACOUSTIC LAYER MODE PROPAGATION ALONG ZNO/SI STRUCTURES.

The influence of a bias electric field on the phase velocity of acoustic layer modes propagating along a ZnO piezoelectric film overlaying a silicon substrate is analyzed. The bias electric field is applied across the ZnO film by means of thin metallic electrodes deposited at the ZnO/Si interface and on the top of the film. Measurements of the change in phase velocity of the acoustic waves, as a function of the bias field intensity, were performed on the acoustic modes propagating along the layered structure for three different values of the product between the acoustic wavenumber beta and the layer thickness h. The fractional changes in the phase velocity depend on the value of the parameter beta h and on the acoustic mode considered; the measured values range from -1. 77 multiplied by 10**-**6 to 7. 05 multiplied by 10**-**6 for a bias electric field of 1 V/ mu m.