Surface acoustic wave ultraviolet sensors based on ZnO nanorods

This study aims at developing a ultraviolet (UV) sensor module which could operate at room temperature by combining a two-port surface acoustic wave (SAW) resonator and ZnO nanorods. The SAW resonator is fabricated based on 128°YX-LiNbO₃ substrate by micro-electro-mechanical system process. The operating frequency is designed to be 145 MHz. The ZnO nanorods are coated on the delay line region of the SAW resonator by aqueous method as sensing film, and their properties are analyzed by scanning electron microscope (SEM) and x-ray diffraction (XRD). The amplifier circuit is designed by simulation software, and a dual delay line configuration is constructed for reducing effects from environmental fluctuation. Finally, the UV sensor module is tested under UV light of 380 and 300 nm wavelengths with various power densities. Results show that the frequency shift increases linearly with power density. The sensitivities to 380 nm and 300 nm UV lights are 19 and 393 Hz·cm²/μW respectively. The experiments prove that the developed UV sensor module has extraordinary advantages, large sensitivity, high stability, good repeatability, and linear relation, on sensing UV light at room temperature.