Stress pattern on the electrode/substrate interfaces in SAW-devices

Recently we have shown that a combined Finite Element Method/Boundary Element Method (FEM/BEM) is capable of analyzing the mass loading effects in SAW-devices. In addition we have demonstrated that employing the Floquet-theorem in conjunction with FEM/BEM is an efficient tool for the treatment of periodic boundary value problems. This efficiency results from the fact that the state of vibration of the periodic system can be described by the knowledge of the field pattern in a fundamental cell. In the present work the mentioned method is extended in order to compute periodic SAW-IDTs containing more than one massive electrode per period. The theory is applied to calculate the stress patterns along the electrode/substrate interfaces. The stress distributions on LiNbO₃-, LiTaO₃-, and quartz-substrate surfaces, which are mechanically loaded by rectangularly shaped aluminum and gold electrodes are presented. For a variety of periodic structures the corresponding dispersion diagrams are calculated