Effects of reductive annealing on insulating polycrystalline thin films of Nb-doped anatase TiO₂: recovery of high conductivity

We studied the effects of reductive annealing on insulating polycrystalline thin films of anatase Nb-doped TiO₂ (TNO). The insulating TNO films were intentionally fabricated by annealing conductive TNO films in oxygen ambient at 400 °C. Reduced free carrier absorption in the insulating TNO films indicated carrier compensation due to excess oxygen. With H₂-annealing, both carrier density and Hall mobility recovered to the level of conducting TNO, demonstrating that the excess oxygen can be efficiently removed by the annealing process without introducing additional scattering centers. (paper)