“Skyrmions in confined spaces: A local-scale SPM analysis”

在这个项目中，我们将我们专用的扫描探针（SPM）方法（即磁力显微镜（MFM），压电力显微镜（PFM）和开尔文探针力显微镜（KPFM）等）应用于skyrmion （SKY）薄膜和纳米结构的基本分析。此外，这些SPM方法也将用于通过电、磁和机械手段在这些薄膜中局部或全局诱导SKY操纵。因此，我们在研究B20、Cu2OSeO3和GaV4S8-(GVS)族块状材料表面的SKYs和skymion晶格（SkLs）方面积累了丰富的SPM经验。GVS系统是非常有利的，因为它是多铁性半导体，这对两者都有利，可以探索薄膜中铁电和磁性织构（SkLs）的相互作用，包括体和界面dzyaloshinskii - moriya相互作用（DMI）的贡献，以及仅通过电手段诱导磁性SKY织构的变化。本文探讨的第三种场刺激方式（除电和磁外）是机械应力，通过外延错配或安装在压电基板载体上进行线性收缩/膨胀时施加到薄膜上。这些操作都将在现场进行，因此在记录这种薄膜的扩展相图时提供了额外的自由度。该项目的核心重点在于gvs家族的薄膜样品，这些样品将以降维的方式制备，即局限于二维（2D）、一维和零维纳米结构的样品。这是通过应用4种不同的制备路线来实现的，即两种自上而下和两种自下而上的策略：通过聚焦离子束铣削或化学机械抛光来实现薄片状薄膜，目标是达到~50纳米厚的独立薄膜。自下而上的方法包括脉冲激光沉积生长GVS样品和使用多晶GVS的单粒作为0D纳米结构。这里介绍的一个特色是楔形样品切割，允许在埋藏界面上通过SPM原位研究不同的竞争相互作用。此外，我们还将SPM研究重点放在第二类薄膜SKY材料上，即SrIrO3 / SrRuO3多层材料。与gvs型样品相反，单个（单）层之间的界面DMI是我们这里的重点。再次，实现了SPM方法的全面分析和对天空的局部操纵。注意，研究这两种突出的新型样品系统，即gvs型和氧化物薄膜，将通过应用我们详细阐述的SPM方法而独特地成为可能；迄今为止，还没有其他技术（无论是真实空间还是往复式空间）能够对这些纳米级系统提供如此深入的了解。因此，我们的方法可能同样适用于该SPP中的其他潜在材料。

In this project, we apply our dedicated scanning-probe (SPM) methods (i.e. Magnetic Force Microscopy (MFM), Piezoelectric Force Microscopy (PFM), and Kelvin Probe Force Microscopy (KPFM), etc.) to the fundamental analysis of skyrmion (SKY)-hosting thin-films and nanostructures. Additionally, these SPM methods will also be used to either locally or globally induce SKY manipulation in these thin films, both by electrical, magnetic, and mechanical means. We hence profit here from our vast SPM experience having investigated SKYs and skyrmion lattices (SkLs) at the surface of the B20, the Cu2OSeO3, and GaV4S8-(GVS)-family-type bulk materials. The GVS systems are very favorable, since being multiferroic semiconductors, which is in favor for both, exploring the mutual interplay of ferroelectric and magnetic textures (SkLs) in thin-films including the contribution of bulk and interfacial Dzyaloshinskii-Moriya-interaction (DMI), as well as inducing changes in the magnetic SKY texture solely by electrical means. A third way of field stimuli (beyond electrical and magnetic) that is explored here is mechanical stress, as exerted onto the thin film either through epitaxial misfit, or when being mounted onto a piezoelectric substrate carrier for linear contraction / expansion. These manipulations will all be performed in-situ, hence providing additional degrees of freedom when recording the extended phase diagrams of such films. The central focus in this project lies on thin-film samples of the GVS-family that will be prepared with reduced dimensions, i.e. samples confined to 2-dimensional (2D), 1D, and 0D nanostructures. This is realized by applying 4 different preparation routes, i.e. two top-down and two bottom-up strategies: thinned-down bulk thin films will be realized either through Focused-Ion-Beam -Milling or Chemical-Mechanical-Polishing with the goal to reach ~50-nm-thick, free-standing thin films. The bottom-up approaches include the GVS-sample-growth by Pulsed Laser Deposition and using single grains of polycrystalline GVS as 0D nanostructures. A specialty introduced here are wedge-like sample-cuts, that allow to in-situ investigate the different competing interactions by SPM at buried interfaces. In addition, we focus our SPM research also on a second class of thin-film SKY materials, i.e. SrIrO3 / SrRuO3 multilayers. In contrast to the GVS-type samples, interfacial DMI between individual (mono)layers stands in our focus here. Again, the full analysis by the SPM methods as well as the local manipulation of SKYs will be realized. -- Note that investigating these two prominent and novel sample systems, i.e. the GVS-type and oxide thin-films, will uniquely be possible through applying our elaborated SPM methods; no other (real or reciprocal-space) technique is known to date that might deliver as much insight into these nanoscale systems. Hence, our methodologies might equally be applied to other prospective materials within this SPP.