Surface acoustic wave propagation in aluminium nitride-unpolished freestanding diamond structures

Abstract

High-quality surface acoustic wave (SAW) filters based on aluminum nitride (AlN)/diamond layered structures were prepared using the nucleation side of polycrystalline chemical vapor deposition (CVD) diamond, removed from a silicon substrate by wet etching. Highly oriented AlN thin films with optimized piezoelectric properties and with various thicknesses were sputtered onto the nucleation side of freestanding diamond. The effect of AlN thickness on the SAW phase velocity, the coupling coefficient, and the device characteristics were investigated. Experimental results show that the Rayleigh wave and the higher modes are generated. These results agree well with calculated dispersion curves and demonstrate that a high electromechanical coupling coefficient together with a high phase velocity can be obtained by using the nucleation side of freestanding CVD diamond laye