Experimental observation of high velocity pseudo-SAWs in ZnO/diamond/Si multilayers

In the past few years, high-velocity surface acoustic wave (SAW) devices have been demonstrated using multilayers containing diamond. These devices have exhibited SAW phase velocities as large as 10 km/s. The high velocities attainable in diamond-based multilayer systems enables the fabrication of high frequency (>2 GHz) SAW devices without requiring submicron device fabrication technologies. Furthermore, higher velocity pseudo-SAWs (PSAWs) with theoretically calculated velocities approaching 18 km/s have also been predicted. In this work, high velocity pseudo-SAWs have been experimentally observed in a ZnO/diamond/Si multilayer. The fabricated SAW devices were delay line structures with uniform transducers on the ZnO surface, and metal shorting planes at the ZnO/diamond interface. Electrical characterization has been made via RF probing, and SAW and PSAW responses have been observed. Of particular interest is a high velocity PSAW with a phase velocity in excess of 16 km/s. The results are in good agreement with simulated dispersive relationships for this multilayer system.