Electrical characterization of band gap states in C-doped TiO2 films -: art. no. 052111

We report on band gap states in C-doped TiO2 films that were prepared by oxidative annealing of sputtered TiC films at 550 degrees C in flowing O-2 gas. Deep-level optical spectroscopy measurements revealed three deep levels located at similar to 0.86, similar to 1.30, and similar to 2.34 eV below the conduction band. The first level is probably attributable to the intrinsic nature of TiO2, whereas the latter two levels are newly introduced by the C-doping. In particular, the pronounced 2.34 eV band contributes to band gap narrowing by mixing with the O 2p valence band. Additionally, the 0.86 and 1.30 eV levels can be active as an efficient generation-recombination center. (c) 2005 American Institute of Physics.