Impact of O2/Ar gas ratio on the DC reactive magnetron sputtered NiO thin films for ultrafast detection with high sensitivity and selectivity towards H2S gas

Abstract

H2S is one of the most hazardous gases, causing several serious health consequences. In the present work, room temperature DC reactive magnetron sputtered NiO thin films were prepared on alumina substrate to detect H2S gas. The O2/Ar gas ratio (10 % and 20 %) influenced the presence of defects (Ni3+/Ni2+) as investigated by XPS studies, and had a substantial impact on the H2S gas sensing performance. The NiO thin film deposited at 20 % O2/Ar ratio exhibited highly improved sensing compared to the film deposited at 10 % O2/Ar ratio. The highest SR ∼14.8 at 350 °C with an ultrafast response time (35s)/recovery time (14s) was achieved for the NiO thin film prepared at 20 % O2/Ar ratio towards 100 ppm H2S gas. An excellent SR ∼5.8 was obtained at a relatively low Top of 175 °C. Further, the high sensitivity and selectivity of NiO thin films make them a prospective material for low ppm (∼3 ppm) H2S gas detection.