Shear-horizontal-type surface acoustic waves on quartz with Ta2O5 thin film

In this paper, the propagation characteristics of two modes of surface acoustic waves (SAWs) on ST quartz with a tantalum pentoxide (Ta₂O₅) thin film are investigated theoretically and experimentally. One is the pure shear-horizontal (SH) wave and the another is the Love-wave-type SAW converted from the leaky SAW (LSAW). For these SAWs, stronger energy trapping effects on the surface can be expected by loading the substrate with the TA₂O₅ thin film, because this film has a relatively high density. In fact, the film thickness of the Ta₂O₅ film required to obtain the minimum insertion loss and the maximum K² for the SH wave on ST-90°X quartz is around 0.01 λ, which is approximately one-fourth of that reported for silicon dioxide film. Furthermore, the attenuation of the LSAW on ST quartz was reduced by loading with the Ta₂O₅ film because the LSAW becomes the Love-wave-type SAW without attenuation.