Analysis of Leaky Surface Acoustic Waves Propagating on Piezoelectric Substrates of Finite Thickness

A numerical analysis of the propagation characteristics of leaky surface acoustic waves is presented, taking into account the finite thickness of piezoelectric substrates. In the analysis, all the 8 plane waves in the substrate are superposed to fulfill the boundary conditions on both surfaces of the substrate. The computational result for LST-cut quartz substrate shows that a first leaky wave splits into even and odd modes when the thickness is reduced. In contrast, the computational result for (90°, 90°, 31°)-cut LiTaO3 substrate shows that many propagation modes exist depending on the substrate thickness, where each velocity approaches that of the longitudinal wave for smaller thickness.