Mechanism of Visible Photoactivity of F-Doped TiO₂

We calculate the electronic structure and optical properties of F-doped anatase TiO₂. The results indicate that the band gap of F-doped TiO₂ increases slightly compared with the pure TiO₂. However, it is interesting that the visible absorption of F-doped TiO₂ located between 600 and 700 nm is observed, and it enhances gradually with the increasing F concentration. Furthermore, according to the results of densities of states and imaginary part of dielectric functionε₂(ω), we propose that the transition between Ti 3d and Ti 3d states may be responsible for the visible absorption, but not the band gap narrowing.