Understanding and controlling self-organized stripe pattern formation in vanadium dioxide

对氧化物材料的持续快速探索已经导致了诸如界面超导性、磁阻和电开关现象等壮观效应的发现。这开辟了氧化物电子学和自旋电子学的技术前景。在这里，除了从硅基前辈继承的传统器件类型的发展之外，还创造了全新的功能元件。然而，不仅功能材料本身，而且界面性质和复杂的异质结构的单原子层规模上的昂贵的制备是至关重要的。二氧化钒（VO 2）是一种具有巨大技术潜力的功能材料，因为它在室温附近具有金属-绝缘体转变。该项目解决了VO 2在外延应变下的应变弛豫机制，这可能导致复杂的相分离现象，如由金属和绝缘区域组成的条纹图案的自组织形成，从而产生本征界面。此外，该项目致力于研究在多大程度上可以从这些效应中获得复杂异质结构的替代路线。从应变相关的形成自组装条纹图案在复杂的氧化物，这些条纹图案的微观尺度上进行了研究，以获得基本的见解，在其物理性质。重点在于几何形状对这种条纹图案的稳定性以及它们的结构和电学特性及其操纵的影响。特别是，该项目旨在首次实现氧化物电子学中全新的器件概念。在这里，内在界面的出现是由几何功能化控制的：器件功能性来自于外部电场对这些界面的后续操作。现代互补显微镜技术和微米至纳米尺度的目标结构的结合用于同时获得相关氧化物的电子和结构特性的见解，并开发用于未来氧化物电子学应用的创新功能元件。

The ongoing rapid exploration of oxide materials has led to the discovery of effects as spectacular as interface superconductivity, magnetoresistance, and electrical switching phenomena. This has opened up the technological perspective of oxide electronics and spintronics. Here, in addition to the development of conventional device types inherited from silicon-based predecessors, entirely novel functional elements have been created. However, not only the functional materials themselves but also the interfacial properties and the costly preparation of complex heterostructures on the scale of single atomic layers are of vital importance. Vanadium dioxide (VO2) is a functional material with a tremendous technological potential due to an metal-insulator transition close to room temperature. This project addresses strain relaxation mechanisms in VO2 under epitaxial strain, which can lead to complex phase separation phenomena like the self-organized formation of stripe patterns consisting of metallic and insulating regions and hence yield intrinsic interfaces. Further, the project is dedicated to the question to what extent an alternative route to complex heterostructures can be obtained from these effects. Starting from the strain-dependent formation of self-assembled stripe patterns in a complex oxide, these stripe patterns are investigated on a microscopic scale to gain fundamental insights in their physical properties. The focus lies on the influences of the geometric shape on the stability of such stripe patterns and on their structural and electrical properties and their manipulation.In particular, this project aims for the first implementation of entirely new device concepts in oxide electronics. Here, the emergence of intrinsic interfaces is controlled specifically by geometric functionalization: the device functionality arises from the subsequent manipulation of such interfaces by external electric fields. A combination of modern, complementary microscopy techniques and targeted structuring on the micrometer to nanometer scale is used to simultaneously obtain insights in the electronic and structural properties of correlated oxides and develop innovative functional elements for applications in future oxide electronics.