Functionalizing electronic and magnetic properties in oxide thin films and heterointerfaces: electric polarization and polar discontinuity

氧化物材料与层状结构的集成通常导致层和/或界面的有趣的、意想不到的电子和磁性。观察到的现象通常是外在的，例如，由相互扩散、缺陷和杂质引起。在这个建议中，我们计划调查两种类型的内在机制-和他们可能的相互作用-，最近成为焦点的一般手段来控制薄膜和界面的电子和磁性。第一个是“电子重建”，即，电荷向界面的重新分布，以补偿当具有不同极性性质的材料组合成分层结构时由于极性不连续性而引起的静电势。第二个是-伴随着结构重排-电极化，其可以被触发以补偿作为电子重构的替代或与电子重构竞争的内置电势，或者在铁电膜材料中自发形成。对于要研究的材料选择，这些机制应该导致厚度相关的磁跃迁，自旋极化界面电子系统和特殊的电子层和界面特性，使托管异质结光致发光活性。在每种情况下，工作中的微观机制应通过先进的电子能谱和显微镜方法的组合方法来阐明。

The integration of oxide materials with layered architectures often leads to intriguing, unexpected electronic and magnetic properties of layers and/or interfaces. Often the observed phenomena are of extrinsic nature and, e.g., caused by interdiffusion, defects, and impurities. Within this proposal we plan to investigate two type of intrinsic mechanisms – and their possible interplay –, which recently came into focus as generic means to control the electronic and magnetic properties of thin films and interfaces. The first is ‘electronic reconstruction’, i.e., the redistribution of charge to the interface in order to compensate the electrostatic potential due to the polar discontinuity when materials with different polar nature are combined in a layered architecture. The second is – concomitant with a structural rearrangement – electric polarization that either can be triggered to compensate a built-in potential as an alternative to or in competition with electronic reconstruction or forms spontaneously in a ferroelectric film material. For the materials selection to be studied these mechanisms are supposed to lead to thickness dependent magnetic transitions, spin-polarized interface electron systems and peculiar electronic layer and interface properties that make the hosting heterostructures photovoltaically active. The microscopic mechanisms at work in each case shall be elucidated by a combined approach of advanced electron spectroscopy and microscopy methods.