The oxygen sensing properties and mechanisms of M-doped α-Ti3O5 thin films (M = Ce, W ions)

In this paper, the oxygen sensing properties (oxygen sensitivity, response time, resistivity–temperature relation, and stability) of M-doped α-Ti3O5 thin films (M=Ce, W ions) are studied. The results show that both doping ions can increase the sensitivity and decrease response time, whereas distinct differences exist in other properties. The doping of Ce ion raises the structure stability but has little effect on resistivity–temperature coefficient. W ion doping, on the other hand, decreases the resistivity–temperature coefficient, but cannot promote the structure stability. By further analysis, two routes improving the oxygen sensing properties are found. One is by increasing active sites on the surface of the materials, i.e. W, which have low adsorption activation energy to gas and tend to be enriched on the surface of materials. The other way is to accelerate the diffuse rate of electrons between the surface and the inside of the film, i.e. Ce, which facilitates the diffusion of electron or hole in the materials.