Dispersive properties of the fundamental rayleigh wave mode (M ₁₁) in a heteroepitaxial zinc oxide film on a sapphire substrate

The dispersion characteristics of an anisotropic ZnO layer on an anisotropic sapphire substrate have been calculated for the fundamental Rayleigh mode. A typical example of the group delay as a function of frequency is illustrated. The time-bandwidth products for the linear regions of the group delay-frequency curves are tabulated. For the cases studied, it has been found that using the basal plane of ZnO on y-cut sapphire with propagation direction at right angles to the trigonal axis of sapphire yields the largest time-bandwidth product (902/in. for a layer thickness of 4μm).