Abstract Cation vacancies play an important role in creating new functionalities in complex oxides. Directly identifying the cation vacancies at the atomic scale is thus key to addressing quantum phenomena related to acceptor states. Here, atomic-scale identification of invisible cation vacancies at an oxide interface via energy-dispersive X-ray spectroscopy (EDX) spectrum imaging is demonstrated. At the homointerface of SrTiO3 (STO) film and a Nb-doped SrTiO3 substrate, the veiled behavior of cation vacancies of Sr and Ti is revealed by the approach for the first time; they are found to reside on their sublattices within the first three or four unit cells of the film in the absence of oxygen vacancies. Theoretical calculations show that two-dimensional electron gas with three unit-cells at the Nb:STO/STO interface is formed by the charge transfer, which leads to the spontaneous formation of cation vacancies for charge compensation, and induces the lattice distortion as well. The results suggest that our EDX approach is useful for obtaining atomic-site-specific information on point defect chemistry with unparalleled precision, which facilitates a path towards atomically precise defect engineering.

中文翻译：

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氧化物同质界面处不可见阳离子空位的原子级识别

摘要 阳离子空位在复杂氧化物中创造新功能方面发挥着重要作用。因此，在原子尺度上直接识别阳离子空位是解决与受体态相关的量子现象的关键。在这里，证明了通过能量色散 X 射线光谱 (EDX) 光谱成像对氧化物界面处不可见阳离子空位的原子级识别。在 SrTiO3 (STO) 薄膜和 Nb 掺杂的 SrTiO3 衬底的同质界面上，该方法首次揭示了 Sr 和 Ti 阳离子空位的隐蔽行为；在没有氧空位的情况下，它们被发现存在于薄膜的前三个或四个晶胞内的亚晶格上。理论计算表明，在 Nb:STO/STO 界面处具有三个晶胞的二维电子气是由电荷转移形成的，这导致自发形成用于电荷补偿的阳离子空位，并引起晶格畸变。结果表明，我们的 EDX 方法可用于以无与伦比的精度获取有关点缺陷化学的原子位点特定信息，这有助于实现原子级精确缺陷工程。