First-principles study of native defects in anataseTiO2

Abstract

Native point defects in anatase $\mathrm{Ti}{\mathrm{O}}_{2}$ are investigated by using first-principles pseudopotential calculations based on density-functional theory (DFT). Antisite defects, namely, Ti-antisite $({\mathrm{Ti}}_{\mathrm{O}})$ and O-antisite $({\mathrm{O}}_{\mathrm{Ti}})$, have high formation energies and are hence unstable. In contrast, all other fundamental native defects (${\mathrm{Ti}}_{i}$, ${\mathrm{O}}_{i}$, ${V}_{\mathrm{Ti}}$, and ${V}_{\mathrm{O}}$) have low formation energies. In particular, titanium interstitial $({\mathrm{Ti}}_{i})$ is a quadruple donor defect with lowest formation energy in $p$-type samples, whereas Ti vacancy $({V}_{\mathrm{Ti}})$ is a quadruple acceptor defect with lowest formation energy in $n$-type samples. Interstitial oxygen $({\mathrm{O}}_{i})$ would spontaneously and strongly bind to lattice oxygen, resulting in a neutral ${\mathrm{O}}_{2}$ dimer substituting on one O site. None of the four low-energy defects have energy levels inside the DFT band gap.