A novel thickness-shear mode resonator using a LiNbO3 plate with an inversion layer

The previous investigations showed that a local domain inversion takes place when bare LiNbO₃ plates undergo heat treatment at temperatures higher than 1070°C. The LiNbO₃ plates with an inversion layer have been used to fabricate piezoelectric bulk acoustic wave devices. The researches on the application of inversion layer piezoelectric devices mainly focused on high frequency ultrasonic transducers working on the thickness extensional mode. The research on inversion layer devices working on the thickness shear mode has not been reported. In this work, several experiments were done to investigate the characteristics of the inversion layer device working on the thickness shear mode. It is found that when the device works on the 2nd harmonic of the thickness shear mode under the role of the inversion layer, spurious modes decrease obviously. The mechanism of suppressing spurious modes through the inversion layer was analyzed. Therefore, bulk acoustic wave devices with an inversion layer working on the thickness shear mode have a good prospect in sensors and resonators.