Hydrogen Gas Sensor Based on Nanocrystalline SnO(2) Thin Film Grown on Bare Si Substrates

In this paper, high-quality nanocrystalline SnO(2) thin film was grown on bare Si (100) substrates by a sol–gel method. A metal–semiconductor–metal gas sensor was fabricated using nanocrystalline SnO(2) thin film and palladium (Pd) metal. The contact between Pd and nanocrystalline SnO(2) film is tunable. Ohmic barrier contact was formed without addition of glycerin, while Schottky contact formed by adding glycerin. Two kinds of sensor devices with Schottky contact were fabricated (Device 1: 8 h, 500 °C; Device 2: 10 h, 400 °C). The room temperature sensitivity for hydrogen (H(2)) was 120 and 95 % in 1000 ppm H(2), and the low power consumption was 65 and 86 µW for two devices, respectively. At higher temperature of 125 °C, the sensitivity was increased to 195 and 160 %, respectively. The sensing measurements were repeatable at various temperatures (room temperature, 75, 125 °C) for over 50 min. It was found that Device 1 has better sensitivity than Device 2 due to its better crystallinity. These findings indicate that the sensors fabricated on bare Si by adding glycerin to the sol solution have strong ability to detect H(2) gas under different concentrations and temperatures.