Study on 36YX-LiTaO3/36Y90X-Quartz Structure for SH-SAWsensor Application

Shear horizontal surface acoustic wave (SH-SAW) devices have been applied to sensors that detect physical quantities of liquids, such as viscosity, relative permittivity, and loaded mass on the surface. Recently, substrates bonded to piezoelectric crystals have been used as filters. In this study, sensor applications of substrates bonded with piezoelectric crystals are discussed. Specifically, the sensor sensitivity of SH-SAWs on single 36°YX- LiTaO
3
(36YX-LT), single 36°Y90
^o
X-quartz (36Y90X-Qz), and 36YX-LT/36Y90X-Qz substrates was determined using the finite element method. The sensitivity of the 36YX-LT/36Y90X-Qz substrate to mass loading was equivalent to that of the single 36Y90X-Qz substrate. In other words, the bonding of 36YX-LT to 36Y90X-Qz improved the sensitivity of the sensor to the mass loading of a single 36YX-LT substrate. Sensor sensitivity to the relative permittivity depends on the electromechanical coupling factor (K
²
). The SH-SAW on a 36YX-LT/36Y90X-Qz substrate is highly sensitive to relative permittivity.