Abstract
AbstractIn a surface acoustic wave substrate with a “piezoelectric thin‐film/substrate” configuration, the temperature coefficients of the acoustic constants of the Ta2O5 and ZnO thin films were determined by means of the least square method based on the experimental values of the temperature coefficients of the acoustic constants. Also, with regard to the two‐layered model of a “piezoelectric thin‐film/piezoelectric thin‐film/substrate” configuration, the surface acoustic wave speed, electromechanical coupling coefficient and temperature characteristics were computed and the combinations of the film thicknesses were derived for a first‐order zero‐temperature coefficient. Further, it is recognized that the ZnO thin film and the Ta2O5 thin film have second‐order delay time temperature dependences with opposite signs and then a method is proposed for controlling the first‐ and second‐order temperature coefficients in a two‐layered substrate. It is found experimentally and theoretically that there exists a highly stable substrate which exhibits a third‐order characteristic at an appropriate film thickness.
Published Version
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