Investigation of properties of surface acoustic waves generated by periodically patterned ZnO on silicon substrate

• Method of SAW transduction in Si substrate using periodically patterned ZnO film proposed.
• Bulk modes in periodic ZnO pattern couple to Si substrate to generate surface modes.
• Characteristics of proposed patterned-ZnO/Si and conventional ZnO/Si devices compared.
• Proposed patterned-ZnO/Si device shown to have high SAW velocity with high coupling coefficient.

The paper presents the characteristics of vertically polarized surface waves generated in silicon substrate by acoustic coupling of bulk waves excited in a periodically patterned ZnO film on silicon. The finite element simulations are performed on the proposed patterned-ZnO/Si structure and vertically polarized modes in silicon are found to be dominant in the frequency dependent analysis. The generated modes in silicon are concentrated near the surface within a wavelength depth and exhibit surface wave properties. Dispersion curves of phase velocity and coupling coefficient for the surface modes are reported. The results indicate high electromechanical coupling coefficient of 6.4% as well as high phase velocity of 5332 m/s for the surface mode generated in silicon owing to the acoustic coupling of the first order bulk mode in ZnO pattern observed at ZnO height to wavelength ratio of 0.19.