Excitation of 1.1-GHz surface acoustic waves in a ZnO/Al2O3 structure

The generation of Rayleigh and Sezawa SAWs is investigated experimentally in layered structures comprising sapphire substrates cut on the 0001 line, interdigital transducers (25 pairs of 1.5-micron-wide 400-micron-aperture Al electrodes spaced 400 microns apart), and 1-micron-thick ZnO piezoelectric films applied over the entire plate surface and then etched back photolithographically to cover only the electrodes. The frequencies, velocities, and propagation losses of the Rayleigh SAWs are given as 830 MHz, 5 km/s, and up to 500 dB/cm, respectively; the corresponding values for Sezawa SAWs are 1.1 GHz, 6.6 km/s, and 200-250 dB/cm, indicating the advantages of Sezawa SAWs in this type of layered structure.