Ab-initio study of indium, nitrogen codoping effect on the structure and properties of TiO₂

With indium and nitrogen as a pair of dopants, different substitutional defects are induced in the structure of anatase TiO₂. Along with substitutional point defects, oxygen vacancy is created for charge compensation/stabilization of the defect induced system. The In 5p states associated with the indium are coupled with the O 2p states narrowing the band gap of TiO₂, and inducing visible light absorption. Nitrogen doping in TiO₂ created isolated N 2p stated above the valence band maximum. With respect to the position of dopants, three different In, N co-doped models are introduced. Moreover, the In, N compensated co-doped configuration is also developed. The In 5p and N 2p states of the dopants are strongly coupled with the host O 2p states reducing the band of TiO₂. The indium and nitrogen doped 5.477 Å apart from each other in the lattice of TiO₂ (anatase) provided maximum absorption in the visible regime among the codoped models. The theoretical findings can explain the experimental observations and widen the applications spectrum of TiO₂. (paper)