Propagation of Bleustein-Gulyaev waves in piezoelectric layered structures with initial stress

Layered structures, especially thin film/coating substrate systems play important roles in micro-electro-mechanical system and microelectronics packages. Many surface acoustic wave (SAW) devices/sensors adopt the layered structures with a piezoelectric layer deposited on the substrate to achieve high performance. Surface electro-acoustic waves (Bleustein-Gulyaev waves) have very practical importance in many signal transmission, signal processing and information storage applications. In piezoelectrics, the interaction between elastic and electric field in such a wave leads to a number of new effects not observable in non-piezoelectric crystals. The propagation behavior of this kind of wave in a piezoelectric layered structure with initial stress is taken into account in this paper. Solutions of the mechanical displacement and electrical potential function are obtained for the piezoelectric layer and substrate, respectively, by solving the coupled electromechanical field equations. Influence of the initial stress on the phase velocity of B-G wave propagation and the electromechanical coupling factor corresponding to this surface wave is discussed. It is seen that the phase velocity of B-G wave propagation decreases and the electromechanical coupling factor increases remarkably as the absolute value of initial stress in the layer is greater than 100 MPa. The results reported in this paper are residual stress distribution not only meaningful for the design of SAW devices with high quality, but also effective for evaluating the residual stress distribution in the layered structures.