Propagation characteristics of leaky surface acoustic waves for two thin metal layers on LiTaO3 substrate

Leaky surface acoustic waves (LSAWs) propagating in the crystalline X-direction of rotated Y-cuts of LiTaO₃ substrates are investigated. The effect of two thin isotropic metallic films deposited on the substrate surface is rigorously taken into consideration. The relatively small bulk wave term in the partial wave solution has a phase velocity vector tilted towards the substrate at an angle of 28.5° referred to the substrate surface for 36° YX LiTaO₃. The radiating bulk wave is a slow shear wave (SSW). Taking energy flow characteristics into account, the power flow for greater penetration depths is that of the SSW. Phase velocity and attenuation constant are computed for different metallic film thicknesses and thickness ratios between the two films. The measured results compare favorably with those obtained from the theoretical analysis