Effects of N Concentration on Electronic Structure and Optical Absorption Properties of N-Doped SrTiO<sub>3</sub> from First Principles

Abstract

The nitrogen concentration effects on electronic structures and optical properties of N-doped SrTiO3 have been investigated on the basis of density functional theory (DFT) calculations. Through band structure calculation, a direct band gap is predicted in SrTiO3-xNx. Electronic structure analysis shows that the doping N could substantially lower the band gap of SrTiO3 by the presence of an impurity state of N 2p on the upper edge of the valence band. When the doping level rises, the energy gap has little further narrowing compared with that at lower doping levels. The calculations of optical properties indicate a possible optimum N-doping level in SrTiO3 with a high photo response for visible light. These conclusions are in agreement with the recent experimental results.