Simulation of characteristics of KNbO3/diamond surface acoustic wave

High-frequency Surface Acoustic Wave (SAW) Devices based on diamond that has been realized to date utilize the SiO2/ZnO/diamond structure, which shows excellent characteristics of high phase velocity over 10,000 m/s with zero temperature coefficient, and it has been successfully applied to high-frequency narrowband filters and resonators. In this paper, the characteristics of KNbO3/diamond with the assumption that the KNbO3 film is single crystal have been studied by theoretical calculations to find higher coupling coefficient condition. Calculations are made for the phase velocity and electromechanical coupling coefficient of the Rayleigh wave and its higher mode Sezawa waves. As a result, KNbO3/Ground/diamond is found to offer extremely high electromechanical coupling coefficient up to 38% in conjunction with high phase velocity of 12,600 m/s. This characteristic is suitable for ultra-wide bandwidth applications in high-frequency SAW devices.