The Enhanced H2 Selectivity of SnO2 Gas Sensors with the Deposited SiO2 Filters on Surface of the Sensors

This paper reports a study on the enhanced H-2 selectivity of SnO2 gas sensors with SiO2 on the surface of the sensors obtained via chemical vapor deposition using dirthoxydimethylsilane as the Si source. The gas sensors were tested for sensing performance towards ethanol, acetone, benzene, and hydrogen at operating temperatures from 150 degrees C to 400 degrees C. Our experimental results show that higher selectivity and responses to hydrogen were achieved by the deposition of SiO2 on the surface of the sensors. The sensor with SiO2 deposited on its surface at 500 degrees C for 8 h exhibited the highest response (R-a/R-g = 144) to 1000 ppm hydrogen at 350 degrees C, and the sensor with SiO2 deposited on its surface at 600 degrees C for 4 h attained the maximum response variation coefficient (D = 69.4) to 1000 ppm hydrogen at 200 degrees C. The mechanism underlying the improvement in sensitivity and the higher responses to hydrogen in the sensors with SiO2 on their surface is also discussed.