The surface acoustic wave velocities and electro-mechanical coupling coefficients of AlN thin films

摘要

Problems encountered in measuring the surface-acoustic wave (SAW) properties of layered structures are discussed. The phase-coherent method and the admittance method are used in measuring the dispersion relationship between SAW phase velocity, SAW electromechanical coupling coefficient, and h*k (h is the thickness of AlN thin films on silicon or glass and k is the SAW wavenumber). Measurements show that only the admittance method is valid in measuring the coupling coefficients of layered structures with any kind of interdigital transducers (IDTs). The phase-coherent method can work for thin-film IDTs without counterelectrodes.