Propagations of Rayleigh and Love waves in ZnO films/glass substrates analyzed by three-dimensional finite element method**Project supported by the National Natural Science Foundation of China (Grant No. 11304160), the Natural Science Foundation of Jiangsu Provincial Higher Education Institutions, China (Grant No. 13KJB140008), and the Foundation of Nanjing University of Posts and Telecommunications, China (Grant No. NY213018).

Abstract

Propagation characteristics of surface acoustic waves (SAWs) in ZnO films/glass substrates are theoretically investigated by the three-dimensional (3D) finite element method. At first, for ZnO films/glass substrates, the simulation results confirm that the Rayleigh waves along the [0001] direction and Love waves along the direction are successfully excited in the multilayered structures. Next, the crystal orientations of the ZnO films are rotated, and the influences of ZnO films with different crystal orientations on SAW characterizations, including the phase velocity, electromechanical coupling coefficient, and temperature coefficient of frequency, are investigated. The results show that at appropriate , Rayleigh wave has a maximum k2 of 2.4% in (90°, 56.5°, 0°) ZnO film/glass substrate structure; Love wave has a maximum k2 of 3.81% in (56°, 90°, 0°) ZnO film/glass substrate structure. Meantime, for Rayleigh wave and Love wave devices, zero temperature coefficient of frequency (TCF) can be achieved at appropriate ratio of film thickness to SAW wavelength. These results show that SAW devices with higher k2 or lower TCF can be fabricated by flexibly selecting the crystal orientations of ZnO films on glass substrates.