Theoretical Study on the Point Defects in N-Doped Anatase TiO2

Theoretical Study on the Point Defects in N-Doped Anatase TiO2

In this work, first-principles calculations for the electronic and the optical properties of titanium dioxide (TiO2) with point defects are performed by using a plane wave pseudopotential method in the framework of the density functional theory and the generalized gradient approximation. The point defects, substitutional and interstitial nitrogen, in anatase TiO2 are investigated to understand the origin of the visible-light sensitivity of nitrogen (N)-doped TiO2. The results show that bands originating from substitutional N 2p states appear above the top of the valence band. These states tend to be delocalized and to mix with the valence band as the nitrogen concentration is increased. The optical absorption in the range between 400 and 700 nm is enhanced by the substitutional N impurities. The eect of interstitial N on the electronic and the optical properties of TiO2 depends on the interaction between the nitrogen dopants and the surrounding oxygen. The bonding between N and O introduces a series of localized occupied states under and above the upper valence band, and the electron transitions from these states improve the visible-light absorption of TiO2.

In this work, first-principles calculations for the electronic and the optical properties of titanium dioxide (TiO2) with point defects are performed by using a plane wave pseudopotential method in the framework of the density functional theory and the generalized gradient approximation. The point defects, substitutional and interstitial nitrogen, in anatase TiO2 are investigated to understand the origin of the visible-light sensitivity of nitrogen (N)-doped TiO2. The results show that bands originating from substitutional N 2p states appear above the top of the valence band. These states tend to be delocalized and to mix with the valence band as the nitrogen concentration is increased. The optical absorption in the range between 400 and 700 nm is enhanced by the substitutional N impurities. The eect of interstitial N on the electronic and the optical properties of TiO2 depends on the interaction between the nitrogen dopants and the surrounding oxygen. The bonding between N and O introduces a series of localized occupied states under and above the upper valence band, and the electron transitions from these states improve the visible-light absorption of TiO2.