Ultrahigh-frequency surface acoustic wave transducers on ZnO/SiO₂/Si using nanoimprint lithography

Ultrahigh-frequency surface acoustic wave devices were fabricated on a ZnO/SiO₂/Si substrate using step-and-flash nanoimprint lithography combined with hydrogen silsesquioxane (HSQ) planarization. Excellent critical dimension control was demonstrated for interdigital transducers with finger electrode widths from 125 down to 65 nm. Fundamental and higher-order Rayleigh modes up to 16.1 GHz were excited and detected, which is the highest frequency for ZnO-based transducers on silicon reported so far. Surface acoustic modes were confirmed with numerical simulations. Simulation results showed good agreement with the experimental data.