Longitudinal leaky surface acoustic wave with low attenuation on LiTaO_3 or LiNbO_3 thin plate bonded to quartz substrate

摘要

To obtain a bonded structure with low attenuation for longitudinal leaky surface acoustic waves (LLSAWs), the propagation and resonance properties on a LiTaO3 (LT) or LiNbO3 thin plate bonded to an X-cut quartz substrate were theoretically analyzed. The attenuation of an X-cut 31 degrees Y-propagating LT (X31 degrees Y-LT)/X32 degrees Y-quartz (X32 degrees Y-Q) was calculated to be 0.0005 dB/lambda at the normalized LT thin plate thickness h/lambda = 0.062 (lambda: wavelength) and was lower than that on an X31 degrees Y-LT/AT45 degrees X-Q. Using a finite element method, for the X31 degrees Y-LT/X32 degrees Y-Q, the admittance ratio and Q factor were improved to 120 dB and 53 400 from 62 dB and 1000 for the X31 degrees Y-LT/AT45 degrees X-Q, respectively. Then, the propagation and resonance properties were measured. For the X31 degrees Y-LT/X32 degrees Y-Q, the measured electromechanical coupling factor (K-2) and Q factor increased to 5.6% and 280 from 1.8% and 32 for the single LT, respectively. The temperature coefficient of frequency of the LLSAW was measured to be -26.2 ppm degrees C-1. (C) 2019 The Japan Society of Applied Physics