Propagation characteristics of the SH-SAW on (110)ZnO/(012)LiTaO 3

Single-crystal ZnO films with the c-axis lying in the film plane can be grown on the (012) plane of LiTaO₃ by electron cyclotron resonance-assisted molecular beam epitaxy (ECR-assisted MBE). The ZnO/LiTaO₃ structures offer a high electromechanical coupling factor K² of the shear horizontal-type surface acoustic wave (SH-type SAW) propagating along the X-axis due to an additional contribution of the piezoelectric shear effect of ZnO. In this paper, the propagation characteristics of the SH-SAW propagating along the X-axis in ZnO/rotated Y-cut LiTaO₃ structures are theoretically analyzed considering the polarity relationship between the film and the substrate. Experimental results on the phase velocity and the coupling factor of the SH-SAW are presented and compared with the theoretical ones. The values of K² for the case of the ZnO film grown on the positive surface of the substrate are different from those for the case of the film grown on the negative surface. The value of K² for ZnO/42°-rotated Y-cut LiTaO₃ is about 1.5 times larger than that for the case with no film