Valence-state reflectometry of complex oxide heterointerfaces
Valence-state reflectometry of complex oxide heterointerfaces
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DOI：
10.1038/npjquantmats.2016.13
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发表时间：
2016-09-16
影响因子：
5.7
通讯作者：
Hinkov, Vladimir
中科院分区：
文献类型：
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作者：
Hamann-Borrero, Jorge E.;Macke, Sebastian;Hinkov, Vladimir
过渡金属氧化物异质结构中的涌现现象，如界面超导性和磁性，被归因于电子重构，然而，这是难以检测和测量的。在这里，我们克服了相关的困难，同时解决的电子自由度和区分接口从散装效果，通过实施一种新的方法，共振X射线反射率（RXR）。我们的RXR研究的化学和价态配置文件沿着的极性（001）方向的LaCoO 3薄膜上的NdGaO 3揭示了一个显着的价态重建从Co 3+在散装到Co2+在表面上，与面密度接近0.5 Co2+离子每晶胞。用极性（001）LaAlO 3覆盖的相同膜在其整个厚度上保持Co 3+价态。我们解释这是电子重建的无盖膜中的证据，涉及到0.5e -每单位电池的转移到其氧化镧终止的极性表面的表面下的CoO 2层。
Emergent phenomena in transition-metal-oxide heterostructures such as interface superconductivity and magnetism have been attributed to electronic reconstruction, which, however, is difficult to detect and characterise. Here we overcome the associated difficulties to simultaneously address the electronic degrees of freedom and distinguish interface from bulk effects by implementing a novel approach to resonant X-ray reflectivity (RXR). Our RXR study of the chemical and valance profiles along the polar (001) direction of a LaCoO3 film on NdGaO3 reveals a pronounced valence-state reconstruction from Co3+ in the bulk to Co2+ at the surface, with an areal density close to 0.5 Co2+ ions per unit cell. An identical film capped with polar (001) LaAlO3 maintains the Co3+ valence over its entire thickness. We interpret this as evidence for electronic reconstruction in the uncapped film, involving the transfer of 0.5e -per unit cell to the subsurface CoO2 layer at its LaO-terminated polar surface.