Gas-sensing characteristics of modified-MoO3 thin films using Ti-overlayers for NH3 gas sensors

Thin films of modified MoO3 using Ti-overlayers have been deposited by magnetron sputtering. The gas-sensing characteristics of the sensor element, the influence of the Ti-overlayers and their preparation parameters on the gas-sensitive properties of the sensors have been studied. It was found that the Ti-overlayer is very effective for enhancing the sensitivity and selectivity to NH3 gas. The sensitivity of the sensor is strongly influenced by the process parameters and the thickness of the sputtered Ti-overlayers. The sensor, using a Ti-overlayer thickness of 50 nm, features the highest gas sensitivity towards NH3, while its cross-sensitivity to other gas such as H-2, SO2 and CO is comparatively small. The operating temperature of the sensor is 200 degrees C. (C) 2000 Elsevier Science S.A. All rights reserved.