Application of the GGA-1/2 excited-state correction method to p-electron defective states: the special case of nitrogen-doped TiO2

摘要

One of the issues in applying the generalized gradient approximation-1/2 (GGA-1/2) quasiparticle approximation to correct the excited-state properties in defective semiconductors is determining the cutoff to the self-energy function at the point defect. Pure and large supercells of N-doped rutile TiO2 were studied using this method to correct excited states and find the correct position of the defect states. A relation between the Bader charge at the defect and the self-energy cutoff parameter of the GGA-1/2 method is shown, with the cutoff value in its p-orbital, which optimizes the position of the defect levels. It was found that, upon nitrogen substitution and associated oxygen vacancy formation, an impurity level at 0.40-0.52 eV above the valence band maximum appears. The same result was obtained upon nitrogen substitution and associated background charge. Finally, the method was also applied to other p-orbital defect systems like Si: X (X = N, P, B) to validate the method.