Quasi-thickness-shear waves in thin-film piezoelectric resonators of ZnO and AlN with tilted C-Axis

We study the propagation of Lamb waves in a piezoelectric plate of crystals of class 6mm with tilted c-axis. Dispersion relations for waves in ZnO and AlN plates with a few specific tilting angles of the c-axis are obtained. Displacement amplitude and phase angle distributions along the plate thickness are also calculated. It is shown that for certain values of the tilting angle of the c-axis, there exist long waves with a dominating thickness-shear component. The results further support the possibility of thin-film resonators operating with thickness-shear modes.