Rose Marc-André, Šmíd Břetislav, Vorokhta Mykhailo, Slipukhina Ivetta, Andrä Michael, Bluhm Hendrik, Duchoň Tomáš, Ležaić Marjana, Chambers Scott A, Dittmann Regina, Mueller David N, Gunkel Felix
Institute for Electronic Materials (IWE 2), and Juelich-Aachen Research Alliance for Fundamentals on Future Information Technology (JARA-FIT), RWTH Aachen University, 52074, Aachen, Germany.
Peter Grünberg Institute 7, Forschungszentrum Jülich GmbH, and JARA-FIT, 52425, Jülich, Germany.
Adv Mater. 2021 Jan;33(4):e2004132. doi: 10.1002/adma.202004132. Epub 2020 Dec 2.
The ability to tailor oxide heterointerfaces has led to novel properties in low-dimensional oxide systems. A fundamental understanding of these properties is based on the concept of electronic charge transfer. However, the electronic properties of oxide heterointerfaces crucially depend on their ionic constitution and defect structure: ionic charges contribute to charge transfer and screening at oxide interfaces, triggering a thermodynamic balance of ionic and electronic structures. Quantitative understanding of the electronic and ionic roles regarding charge-transfer phenomena poses a central challenge. Here, the electronic and ionic structure is simultaneously investigated at the prototypical charge-transfer heterointerface, LaAlO /SrTiO . Applying in situ photoemission spectroscopy under oxygen ambient, ionic and electronic charge transfer is deconvoluted in response to the oxygen atmosphere at elevated temperatures. In this way, both the rich and variable chemistry of complex oxides and the associated electronic properties are equally embraced. The interfacial electron gas is depleted through an ionic rearrangement in the strontium cation sublattice when oxygen is applied, resulting in an inverse and reversible balance between cation vacancies and electrons, while the mobility of ionic species is found to be considerably enhanced as compared to the bulk. Triggered by these ionic phenomena, the electronic transport and magnetic signature of the heterointerface are significantly altered.
定制氧化物异质界面的能力已在低维氧化物体系中带来了新特性。对这些特性的基本理解基于电荷转移的概念。然而，氧化物异质界面的电子特性关键取决于其离子组成和缺陷结构：离子电荷在氧化物界面处有助于电荷转移和屏蔽，引发离子和电子结构的热力学平衡。对电荷转移现象中电子和离子作用的定量理解构成了一个核心挑战。在此，在典型的电荷转移异质界面LaAlO₃/SrTiO₃上同时研究电子和离子结构。在氧气环境下应用原位光电子能谱，响应高温下的氧气气氛对离子和电子电荷转移进行解卷积。通过这种方式，复杂氧化物丰富且多变的化学性质以及相关的电子特性都得到了同等的关注。当施加氧气时，界面电子气通过锶阳离子亚晶格中的离子重排而耗尽，导致阳离子空位和电子之间形成反向且可逆的平衡，同时发现离子物种的迁移率与体相相比显著增强。受这些离子现象的触发，异质界面的电子输运和磁特性发生了显著改变。
