Surface acoustic wave characteristics in ZnO thin films deposited on different Silicon-based multilayered substrates

This paper investigates the characteristics of surface acoustic waves (SAWs) in piezoelectric ZnO thin films deposited on various bilayer substrates composed of silicon-derived materials. Finite element analysis is used to study the phase velocities and electromechanical coupling factors K² of the first two fundamental SAW modes, propagating in multilayered ZnO/Si, ZnO/SiC/Si, ZnO/SiO₂/Si, and ZnO/SiN/Si structures. ZnO thin films are grown on these substrates and subsequently characterized using atomic force microscopy (AFM) and X-ray diffraction (XRD) to assess film quality. Among the studied configurations, ZnO/SiO₂/Si demonstrates the best performance, exhibiting well-defined SAW modes, superior crystallinity and enhanced K². ZnO/SiO₂/Si SAW delay line is then fabricated using conventional photolithography and electrically characterized by network analyzer. The response of the device confirms the presence of both Rayleigh and Sezawa modes, aligning with numerical predictions. The findings of this study contribute to the development of high-performance SAW sensors and resonators compatible with silicon and silicon-based technologies.