First principles study on electronic structures and properties of Sn-doped rutile TiO2

Density functional theory calculations have been carried out to determine the effects of Sn doping on the geometrical and electronic properties of rutile TiO2. According to calculations, the effect of Sn on energy band structure depends on its substitutional sites in the rutile lattice. The substitution sites of Sn in rutile TiO2 induces effective reduction of the energy gap, with the energy gap being continuously increased when decreasing Sn doping level. On the other hand, when Sn is in the interstitial site of rutile TiO2, and then this interstitial doping is not energetically preferred, the excitation energy increases slightly compared with the undoped case due to the a significant local structure distortion. The results provide explanations not only for the red-shift of the optical absorption edge in different experiments, but also for the electronic properties of Sn-doped rutile TiO2, with a certain potential use in many fields.