First-principles study of atomic structure and electronic properties of Si and F doped anatase TiO₂

Chemical doping represents one of the most effective ways in engineering electronic structures of anatase TiO₂ for practical applications. Here, we investigate formation energies, geometrical structures, and electronic properties of Si-, F-doped and Si/F co-doped anatase TiO₂ by using spin-polarized density functional theory calculation. We find that the co-doped TiO₂ is thermodynamically more favorable than the Si- and F-doped TiO₂- Structural analysis shows that atomic impurity varies crystal constants slightly. Moreover, all the three doped systems show a pronounced narrowing of band gap by 0.33 eV for the F-doped TiO₂, 0.17 eV for the Si-doped TiO₂, and 0.28 eV for the Si/F-co-doped TiO₂, which could account for the experimentally observed redshift of optical absorption edge. Our calculations suggest that the Si/F-co-doping represents an effective way in tailoring electronic structure and optical properties of anatase TiO₂.