Theoretical Analysis of Electromechanical Coupling Coefficient of Lamb Waves in ZnO/Si Multilayered Piezoelectric Plates

Abstract

Lamb wave devices have been widely used in electro-acoustic and microfluidic devices. In order to improve their performances, the phase velocity dispersion and electromechanical coupling coefficient (ECC) of the Lamb wave should be calculated exactly during designing. Accordingly, this paper aims at analyzing exactly Lamb waves in multilayered piezoelectric plates with distinct electrode arrangements. First, the formulae of effective permittivity were derived based on the transfer matrix method and further was employed to calculate the phase velocity dispersion. The ZnO/Si multilayered plate was taken as the calculation example. The ECCs under distinct electrical boundary conditions were calculated by the Green's function method. Finally, the influences of the silicon thickness on the phase velocity dispersion and ECC are further discussed. Results show that the coupling coefficients deeply depends on the electrode arrangement, and the S0 mode with the electrode arrangements of type D is a better due to its larger velocity and higher coupling coefficient. Moreover, the ECC can be enlarged by reducing the nonpiezoelectric membrane thickness.