Boonchun Adisak, Reunchan Pakpoom, Umezawa Naoto
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.
Department of Physics, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand.
Phys Chem Chem Phys. 2016 Nov 2;18(43):30040-30046. doi: 10.1039/c6cp05798e.
The energetics and electronic structures of native defects in anatase TiO are comprehensively studied using hybrid density functional calculations. We demonstrate that oxygen vacancies (V) and titanium interstitials (Ti) act as shallow donors, and can form at substantial concentrations, giving rise to free electrons with carrier densities from 10 to 10 cm under oxygen-rich and oxygen-poor conditions, respectively. The titanium vacancies (V), 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 TiO. At a typical annealing temperature and under a typical oxygen partial pressure, the carrier concentration is found to be approximately 5 × 10 cm.
利用杂化密度泛函计算对锐钛矿型TiO中本征缺陷的能量学和电子结构进行了全面研究。我们证明，氧空位（V）和钛间隙原子（Ti）作为浅施主，能够以相当高的浓度形成，分别在富氧和贫氧条件下产生载流子密度为10至10 cm的自由电子。被确定为深受主并诱导空穴载流子的钛空位（V），在任何氧化学势下都无法完全补偿源自施主型缺陷的自由电子。即使在极端富氧条件下，由电荷缺陷、电子和空穴载流子之间的电荷中性条件确定的费米能级位于价带最大值上方2.34 eV处，这表明在没有外部掺杂的任何生长条件下都无法实现p型导电性。这与TiO本征n型导电性的常见观察结果一致。在典型的退火温度和典型的氧分压下，发现载流子浓度约为5×10 cm。
