ZnO/quartz structure potentiality for surface acoustic wave pressure sensor

It has been reported that a Rayleigh wave propagating on a zinc oxide film has a relatively low temperature coefficient of frequency (TCF) and a large electromechanical coupling factor (K2). In this study, we investigate the performance of a SAW pressure sensor based on a ZnO/quartz structure. We used the quartz Y–X in this structure owing to the zero TCF value that this quartz produces when it is combined with a thin ZnO film of particular thickness. This film thickness was determined here not only to achieve such zero value, but also to increase the electromechanical coupling coefficient (K2 = 1%) to seven times higher than that of quartz Y–X. The theoretical approach to select the optimal structure is presented, which is followed by discussions on the effect of the operating frequency and on the ZnO film contribution to the pressure sensitivity.