Photo-Deactivated Room Temperature Hydrogen Gas Sensitivity Of Nanocrystalline Doped-Tin Oxide Sensor

Nanocrystalline indium oxide (In2O3)-doped tin oxide (SnO2) thin film is sol-gel dip-coated on the microelectromechanical systems (MEMS) devices as a room temperature hydrogen (H2) sensor. The effect of ultraviolet (UV) radiation on the room temperature H2 gas sensitivity of the present micro-sensor device is systematically studied. It is shown that the exposure to the UV-radiation results in the deterioration of the H2 gas sensitivity of the present sensor, which is in contrast with the earlier reports. Very high H2 gas sensitivity as high as 110×103 is observed, for 900 ppm H2, without exposing the sensor to the UV-radiation. In the presence of UV-radiation, however, the H2 gas sensitivity reduces to 200. The drastic reduction in the H2 gas sensitivity due to the UV-exposure is explained on the basis of the constitutive equation for the gas sensitivity of the nanocrystalline semiconductor oxides thin film sensors