Enhanced response characteristics of SnO2 thin film based NO2 gas sensor integrated with nanoscaled metal oxide clusters

Gas sensor structure based on rf sputtered SnO2 thin film is found to be highly sensitive (Response = 1.4 × 104) toward 10 ppm NO2 gas, but with slow response (∼4 min) and recovery (∼33 min) times. To improve the response and recovery speeds of the sensor, different metal oxide catalysts (WO3, TeO2, Al2O3, NiO, CuO, In2O3, ZnO, TiO2, Ag2O and PdO) in the form of nano-thin micro-clusters have been deposited over SnO2 sensor surface and their effect toward sensing response characteristics of NO2 gas has been studied. Amongst all the catalysts WO3 nano-thin micro-clusters are found to be yielding a high response (5.1 × 104) for low concentration of NO2 gas (10 ppm) at a low operating temperature of 100 °C with a fast response and recovery times of 67 sec and 17 min respectively. On the other hand, TeO2 nano-thin micro-clusters are found to reduce the operating temperature of SnO2 thin film sensor to 90 °C exhibiting comparatively higher response of 2.20 × 104 with faster response and recovery time of 1.25 min and 15.01 min respectively. Formation of n–n junction in WO3/SnO2 sensor besides the spill over of target (NO2) gas molecules over the uncovered surface of sensing SnO2 thin film is found to be advantageous in getting enhanced and faster response characteristics toward NO2 gas.