Theoretical study and finite element simulation of ZnO/GaAs higher-order Lamb waves for microsensor application in liquid media

Abstract

Lamb waves with dominantly longitudinal displacement component have been reported for sensor application in liquid media. However, they are still limited for the fundamental symmetry mode with low plate thickness-to-wavelength (h/) ratio, resulting in large wavelength and low resonance frequency. Here we show the finite element simulation study of higher-order Lamb waves on GaAs and ZnO/GaAs plates. In-plane polarised quasi-longitudinal higher-order Lamb waves are obtained at higher h/ ratio resulting in higher resonance frequencies. The solid-liquid contact simulation shows the confinement of acoustic energy inside the plate. The result demonstrates the suitability of ZnO/GaAs higher-order quasilongitudinal modes for microsensor in liquid media.

Higher-order Lamb waves with quasi-zero surface displacement components on a GaAs piezoelectric plate

“…There are two possible methods in improving the K 2 related to the piezoelectric materials. First, due to weak piezoelectricity in a cubic GaAs plate, a thin-film piezoelectric layer such as ZnO can be deposited on GaAs for piezoelectric field enhancement and signal strength improvement in RW [30] and LW [31] devices. However, the deposition of the thin film will also affect the displacement component profile across the plate, which may increase the displacement on the surface of the plate.…”