Effects of violet-, green-, and red-laser illumination on gas-sensing properties of SnO thin film

We examined the gas-sensing properties of a 10-nm-thick SnO thin film under the illumination of violet, green, and red laser beams at room temperature. A comparison of the gas-sensing outputs of the device after operation in the dark at elevated temperatures (100, 150, and 200 °C) and when illuminated by a laser beam at room temperature indicated that this metal-oxide film had good gas-sensing performance and excellent stability under the illumination of the violet beam. When exposed to several target gases, including NO2, SO2, H2S, and NH3, the SnO thin film was most sensitive to H2S with a minimum concentration of 5 ppm. During the H2S test, a two-step response of the sensor was recorded, which provided information for understanding the effects of chemisorbed and photo-induced oxygen species on the gas-sensing properties of the illuminated sensor. A possible light-induced gas-sensing mechanism of the SnO thin film was proposed and investigated in detail.