Development of NiO-based thin film structures as efficient H2 gas sensors operating at room temperatures

Abstract P-type NiO thin films have been developed on high resistivity Si and SiO 2 substrates by a pulsed laser deposition technique using an ArF ⁎ 193 nm excimer laser at deposition temperature of 300 °C and in 40 Pa partial oxygen pressure. Structures based on such NiO films as host material in the form of Au–NiO Schottky diodes have been subsequently developed under vacuum. In a different procedure, an n-SnO 2 layer has been deposited by a CVD technique on a NiO film to produce a p/n heterojunction. The sensing properties of all above structures have been tested upon exposure to a H 2 flow in air ambient gas at various operating temperature ranging from 30 to 180 °C. For the NiO films, the optimum temperature was about 150 °C exhibiting a sensitivity of 94%. After surface sensitization of NiO by Au the NiO films showed an H 2 response at operating temperature of 30 °C. The sensitivity of p-NiO/n-SnO 2 heterojunction devices was extracted from I – V measurements in air and under H 2 flow mixed in air. In this case a dramatic increase of the sensitivity was achieved at operating temperature of 30 °C for a forward bias of 0,2 V.