Semiconductor MoO3–TiO2 thin film gas sensors

The O2, CO and NO2 gas sensing properties of MoO3–TiO2 thin films have been studied. The sol–gel process was employed to fabricate MoO3–TiO2 thin films onto sapphire and alumina transducers for gas sensing measurements. It was found the MoO3 dominated sensors have a lower optimal operating temperature of 370°C than the TiO2 dominated sensors. The response of the sensors was stable and reproducible at operating temperatures below 400°C. However, once the films were exposed to temperatures higher than 400°C, repeatable gas sensing results could not be achieved. The low evaporation temperature of MoO3 component of the mixed system is believed to be the cause of the sensors instability and irreversibility at high operating temperatures.