Development of highly sensitive and solar blind surface acoustic wave UV-C photodetector based on the In2O3/Ta2O5 nano-heterojunction and its interface electronics

Abstract

A highly sensitive surface acoustic wave (SAW) ultraviolet-C (UV-C) sensor based on In2O3/Ta2O5 nano-heterojunctions and its interface electronics was developed to detect solar blind corona discharge near high voltage power lines. The SAW sensor, based on pristine In2O3 nanoparticles, exhibits a weaker and slower response to UV-C light. To improve the response to deep UV light, In2O3 nanoparticles/Ta2O5 heterojunctions were formed by depositing Ta2O5 films of different thicknesses (2–10 nm) around the In2O3 nanoparticles via atomic layer deposition (ALD) on the cavity between two interdigital transducers (IDTs) in the SAW delay line. The experimental results show a significantly enhanced sensor response towards UV-C light, which is attributed to a high surface-to-volume ratio, an inhibited recombination rate of the photogenerated electron-hole pairs on the surface of the sensing material owing to Ta2O5 conformal coverage, and well-matched energy bandgap engineering. An empirical mechanism was proposed to elucidate the enhanced sensing behavior of the heterostructure. To observe the frequency shifts in real-time on a PC display, portable interface electronics were developed on a single printed circuit board (PCB) for the SAW UV-C sensor, eliminating the effect of frequency shifts caused by ambient temperature and humidity changes. The sensor characteristics were evaluated based on the size and annealing conditions of the In2O3 nanoparticles and the thickness of the decorated Ta2O5, and the scientific and technical causes and analysis of the results were thoroughly investigated. In the selectivity test, the fabricated sensor exhibited a strong response to a UV-C light beam with a sensitivity of 368.3 (ppm (μW/cm2)−1 at 254 nm, and its spectral response to UV-C light was 3.3 times higher than that under UV-A 365 nm light.