The density of polarity-induced oxygen vacancies ( V O s) at the LaAlO 3 (LAO) surface of LAO / SrTiO 3 (STO) (001) heterostructures (HSs) and the density of induced carriers at the interface are quantitatively investigated. Using chemical equilibrium conditions combined with density-functional-theory calculations of total energy, we set up a model for the densities of the V O s and the carriers, which are a function of the thickness of the LAO film, oxygen pressure, and temperature during the LAO/STO HSs growth. For the HSs with over three LAO unit-cell layers, our results show that the presence of a high density ( ∼ 10 14 cm − 2) of the V O s is inevitable, even for the HSs grown at high oxygen pressures, and the densities of the V O s and the carriers mainly depend on the LAO thickness and slightly on the oxygen pressure and temperature. Our results also demonstrate that the intrinsic doping cannot occur. The stability of the V O s under high oxygen pressures is attributed to the release of electrostatic energy from the polar electric field in the LAO film.

中文翻译：

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极性-非极性钙钛矿异质结构 LaAlO3/SrTiO3 表面不可避免的高密度氧空位

定量研究了 LAO / SrTiO 3 (STO) (001) 异质结构 (HS) 的 LaAlO 3 (LAO) 表面的极性诱导氧空位 (VO s) 密度和界面处诱导载流子的密度。使用化学平衡条件结合总能量的密度泛函理论计算，我们建立了 VO 和载流子密度的模型，该模型是 LAO 膜厚度、氧气压力和温度的函数。 LAO/STO HS 的增长。对于具有三个以上 LAO 晶胞层的 HSs，我们的结果表明，即使对于在高氧压力下生长的 HSs，高密度（~ 10 14 cm - 2）的 VO s 的存在也是不可避免的，并且密度VO s 和载流子的数量主要取决于 LAO 厚度，略取决于氧气压力和温度。我们的结果还表明不会发生本征掺杂。VO s 在高氧压力下的稳定性归因于 LAO 膜中极性电场释放静电能。