title: Energetics of native defects in anatase TiO2: a hybrid density functional study.
abstract: The energetics and electronic structures of native defects in anatase TiO2are comprehensively studied using hybrid density functional calculations. We demonstrate that oxygen vacancies (VO) and titanium interstitials (Tii) act as shallow donors, and can form at substantial concentrations, giving rise to free electrons with carrier densities from 1011to 1019cm-3under oxygen-rich and oxygen-poor conditions, respectively. The titanium vacancies (VTi), identified as deep acceptors and induced hole carriers, are incapable of fully compensating for the free electrons originating from the donor-type defects at any oxygen chemical potential. Even under extreme oxygen-rich conditions, the Fermi level, which is determined from the charge neutrality condition among charge defects, electron and hole carriers, is located 2.34 eV above the valence band maximum, indicating that p-type conductivity can never be realized under any growth conditions without external doping. This is consistent with common observations of intrinsic n-type conductivity of TiO2. At a typical annealing temperature and under a typical oxygen partial pressure, the carrier concentration is found to be approximately 5 × 1013cm-3.
authors: Department of Physics, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand and International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.
authors: Adisak
authors: A
authors: Boonchun
authors: Department of Physics, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand.
authors: Pakpoom
authors: P
authors: Reunchan
authors: International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan and Center for Materials research by Information Integration (CMI2), National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan. umezawa.naoto@nims.go.jp.
authors: Naoto
authors: N
authors: Umezawa