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We have investigated the geometrical structures and electronic properties of Si-doped anatase and rutile TiO2 using spin-polarized density functional theory calculations based on the plane-wave method. Our calculated results show that the valence band maximum has a little raise in substitutional Si to O doped anatase and rutile TiO2, and the Fermi level is pinned in the conduction band edge, indicating typical n-type characteristic of semiconductor. In substitutional Si to O doped anatase TiO2, the transition of electrons excited form the valence band to the conduction band above the Fermi level may induce a redshift of optical absorption edge, while the electron transition energy has no obvious decrease in substitutional Si to O doped rutile TiO2. In substitutional Si to Ti doped anatase TiO2, the electron transition energy from the valence band to the conduction band has a decrease about 0.25eV, which may be responsible for the experimental redshift of optical absorption edge. A decrease of excitation energy about 0.2eV is also observed in substitutional Si to Ti doped rutile TiO2. Our results also indicated that the synthesis substitutional Si to Ti doped anatase and rutile TiO2 is preferred under both O-rich and Ti-rich growth conditions. |
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Keywords:photocatalytic; TiO2; electronic structure; DFT |
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