Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109, USA.
Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109, USA.
Nanoscale. 2017 Jan 19;9(3):1120-1127. doi: 10.1039/c6nr07892c.
Oxygen vacancies are important defects considered to play a central role in the electronic and optical properties of tantalum pentoxide (TaO) films and devices. Despite extensive experimental studies on oxygen vacancies in TaO, the reported defect states are ambiguously identified due to the absence of accurate and conclusive theoretical evidence. Here we investigate the thermodynamic, electronic, and optical properties of oxygen vacancies in amorphous TaO by first-principles calculations based on hybrid-functional density functional theory (DFT). The calculated thermodynamic and optical transition levels are in good agreement with a broad range of diverse measured properties with various experimental methods, providing conclusive evidence for the identification of the defect states observed in experiments as originating from oxygen vacancies. Our calculations also predict the formation of spin-polarized polarons. Our results elucidate the fundamental atomistic properties of oxygen vacancies in various oxidation states as a function of growth conditions and provide guidance to control the properties of TaO films/devices.
氧空位被认为在五氧化二钽（TaO）薄膜和器件的电子和光学性质中起着核心作用，是一种重要的缺陷。尽管人们对 TaO 中的氧空位进行了广泛的实验研究，但由于缺乏准确和确凿的理论证据，报道的缺陷态仍存在歧义。在这里，我们通过基于杂化泛函密度泛函理论（DFT）的第一性原理计算研究了非晶 TaO 中氧空位的热力学、电子和光学性质。计算得到的热力学和光学跃迁能级与各种实验方法测量的广泛多样的性质很好地吻合，为实验中观察到的缺陷态源自氧空位提供了确凿的证据。我们的计算还预测了极化子的自旋极化。我们的结果阐明了不同氧化态下氧空位在不同生长条件下的基本原子性质，并为控制 TaO 薄膜/器件的性能提供了指导。
