Theoretical aspects of GSAW and HVPSAW propagation properties for zinc oxide films on silicon carbide and correlation with experimental data

In this paper, the surface acoustic wave (SAW) propagation properties of sputtered zinc oxide (ZnO) films on single crystal silicon carbide (SiC) recently experimentally characterized are compared with the results of calculations based on published material data for SiC crystal and ZnO film. The two surface modes observed experimentally, a generalized SAW (GSAW) mode and a high velocity Pseudo-SAW (HVPSAW) mode, have been theoretically investigated with various values of the unknown elastic constant C₁₃ of SiC within the interval permitted by the requirement of positive elastic energy in a crystal. For the GSAW mode, the calculated velocity dispersion was essentially insensitive to the value of C₁₃ and consistent with the experimental data. For the HVPSAW mode, a good agreement between the calculated and measured leaky-wave propagation loss versus ZnO film thickness dependencies was observed when the SiC elastic constant C₁₃ was taken near zero. The highest piezoelectric coupling of 5.2% has been theoretically predicted for the first GSAW mode and for the electrode configuration with the IDT at the film-substrate interface and metallized upper surface.