Mechanism of the Sensitivity Enhancement in TiO2 Hollow-Hemisphere Gas Sensors

Abstract

We investigate the mechanism of the sensitivity enhancement in TiO2 hollow-hemisphere gas sensors. Using monolayer close-packed polystyrene microspheres as a sacrificial template, a TiO2 thin film based on a network of ordered hollow hemispheres is formed by room-temperature sputtering deposition and subsequent calcination at 550 degrees C. A thin film gas sensor based on the TiO2 hollow hemispheres exhibits a 225% change in its resistance when exposed to 50 ppm CO at 250 degrees C, whereas a gas sensor based on a flat TiO2 film shows an 85% change. Numerical analysis reveals that the enhancement of the gas sensitivity in the hollow-hemisphere gas sensor is simply the result of an increase in the effective surface area for the adsorption of gas molecules.