Photo‐Deactivated Room Temperature Hydrogen Gas Sensitivity of Nanocrystalline Doped‐Tin Oxide Sensor

Nanocrystalline indium oxide (In 2 O 3 )-doped tin oxide (SnO 2 ) thin film is sol-gel dip-coated on the microelectromechanical systems (MEMS) devices as a room temperature hydrogen (H 2 ) sensor. The effect of ultraviolet (UV) radiation on the room temperature H 2 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 H 2 gas sensitivity of the present sensor, which is in contrast with the earlier reports. Very high H 2 gas sensitivity as high as 11 0×10 3 is observed, for 900 ppm H 2 , without exposing the sensor to the UV-radiation. In the presence of UV-radiation, however, the H 2 gas sensitivity reduces to 200. The drastic reduction in the H 2 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.