Oxygen sensing performance of Nb-doped TiO₂ thin film with porous structure

In this paper, Nb-doped titanium dioxide (TiO₂) porous thin films in application of oxygen sensors were studied. A facile sol-gel method was used to prepare the undoped and Nb-doped TiO₂ thin films. The microstructure and oxygen-sensing behavior were investigated. The results indicate that Nb-doping can retard the phase transition from anatase to rutile and reduce the grain size. The oxygen responses of the thin film can be greatly improved by Nb-doping, which are 73.2 and 78.7 for sample with 6% Nb-doping measured at 700°C in the atmosphere with 2% and 20.9% oxygen, while those for undoped TiO₂ are only 6.5 and 6.6 in the same condition. The 6% Nb-doped TiO₂ thin film also shows the fastest response time of only 1.1 s at 700°C, which is only less than 1/10 of those for the undoped TiO₂ thin film.