Acoustic Wave Propagation Along Piezoelectric Plate Coated with Piezoelectric Films

A novel solid state structure consisting of piezoelectric plate sandwiched between two piezoelectric films is suggested as propagation medium for acoustic waves. Considering, as an example, quartz plate coated with AlN film and with AlN film together with ZnO film, the main characteristics of the Lamb and SH acoustic modes are numerically calculated and compared with each other. It is shown that i) the range of acoustic parameters achievable in structures is wider than that is for an uncoated plate, ii) generation of waves in the plate with one film is accomplished by 12 transducer configurations, while there are 32 configurations to excite the same waves in two film structure, iii) dispersion of the wave velocities and coupling constants depend on the mode order, mode type, film thickness, plate thickness, and transducer configuration. This property makes selection of appropriate modes more flexible. Results of calculations are partially verified experimentally.