Propagation properties of leaky surface acoustic wave on water-loaded piezoelectric substrate

To evaluate acoustical loss mainly due to Rayleigh scattering loss of a thin film material using a line-focus-beam ultrasonic material characterization system, surface acoustic waves (SAWs) were excited and detected using IDTs, the propagation properties of SAWs with and without water loading were measured, and the acoustical losses of amorphous SiO₂ and Ta₂O₅ thin films deposited on 128°YX-LiNbO₃ were evaluated by subtracting the calculated attenuation of leakage loss into water from the measured propagation loss of leaky SAWs (LSAWs) on water-loaded specimens. The results of the evaluation of acoustical losses using LSAWs with the SAW propagation mode of the small leakage loss were in good agreement with the measured propagation loss of the Rayleigh-type SAW corresponding to the acoustical loss.