Intrinsic defects and electronic conductivity of TaON: First-principles insights

Using hybrid functional calculations we show that TaON has different defect properties from the binary tantalum oxide and nitride: (i) instead of O or N vacancies or Ta interstitials, the O-N antisite is the dominant defect, which determines its intrinsic n-type conductivity and the p-type doping difficulty; (ii) the O-N antisite has a shallower donor level than O or N vacancies, with a delocalized distribution composed mainly of the Ta 5d orbitals, which gives rise to better electronic conductivity in the oxynitride than in the oxide and nitride. The phase stability analysis reveals that further oxidation of TaON is possible when the oxygen chemical potential is high (O rich); thus, a low oxygen partial pressure is required to synthesize stoichiometric TaON samples. (C) 2011 American Institute of Physics. [doi:10.1063/1.3664346]