Goodge Berit H, El Baggari Ismail, Hong Seung Sae, Wang Zhe, Schlom Darrell G, Hwang Harold Y, Kourkoutis Lena F
School of Applied and Engineering Physics, Cornell University, Ithaca, NY14853, USA.
Department of Physics, Cornell University, Ithaca, NY14853, USA.
Microsc Microanal. 2022 Feb 22:1-8. doi: 10.1017/S1431927622000125.
As a real-space technique, atomic-resolution STEM imaging contains both amplitude and geometric phase information about structural order in materials, with the latter encoding important information about local variations and heterogeneities present in crystalline lattices. Such phase information can be extracted using geometric phase analysis (GPA), a method which has generally focused on spatially mapping elastic strain. Here we demonstrate an alternative phase demodulation technique and its application to reveal complex structural phenomena in correlated quantum materials. As with other methods of image phase analysis, the phase lock-in approach can be implemented to extract detailed information about structural order and disorder, including dislocations and compound defects in crystals. Extending the application of this phase analysis to Fourier components that encode periodic modulations of the crystalline lattice, such as superlattice or secondary frequency peaks, we extract the behavior of multiple distinct order parameters within the same image, yielding insights into not only the crystalline heterogeneity but also subtle emergent order parameters such as antipolar displacements. When applied to atomic-resolution images spanning large (~0.5 × 0.5 μm2) fields of view, this approach enables vivid visualizations of the spatial interplay between various structural orders in novel materials.
作为一种实空间技术，原子分辨率扫描透射电子显微镜（STEM）成像包含了材料结构有序性的幅度和几何相位信息，后者编码了有关晶格中局部变化和不均匀性的重要信息。这种相位信息可以通过几何相位分析（GPA）来提取，该方法通常专注于弹性应变的空间映射。在这里，我们展示了一种替代的相位解调技术及其在揭示关联量子材料中复杂结构现象方面的应用。与其他图像相位分析方法一样，锁相方法可以用于提取有关结构有序和无序的详细信息，包括晶体中的位错和复合缺陷。将这种相位分析应用于编码晶格周期性调制的傅里叶分量，如超晶格或二次频率峰值，我们在同一图像中提取多个不同序参量的行为，不仅深入了解了晶体的不均匀性，还洞察了诸如反极位移等微妙的新兴序参量。当应用于跨越较大（约0.5×0.5μm2）视场的原子分辨率图像时，这种方法能够生动地可视化新型材料中各种结构有序之间的空间相互作用。
