Lamb wave and plate mode in ZnO/silicon and AlN/silicon membrane - Application to sensors able to operate in contact with liquid

Lamb waves, especially the A(0) mode, can be used to build sensors able to operate in contact with liquid. Nevertheless, some difficulties remain for practical devices. First, we discuss the relevance of the electromechanical coefficient. We present the element of choice of the device characteristic s and the piezoelectric material. We compare two kinds of devices, the firs t is a classical delay line device and the second a resonant device. The be havior of these devices has been controlled using optical visualization of vibration modes. Furthermore, the performance of the devices is experimenta lly tested and advantages of the resonant device are shown. (C) 2000 Elsevi er Science B.V. All rights reserved.