Takamoto Masaya, Seki Takehito, Ikuhara Yuichi, Shibata Naoya
Institute of Engineering Innovation, School of Engineering, The University of Tokyo, Yayoi 2-11-16, Bunkyo-ku, Tokyo 113-0032, Japan.
PRESTO, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan.
Microscopy (Oxf). 2024 Oct 4;73(5):422-429. doi: 10.1093/jmicro/dfae019.
Differential phase contrast scanning transmission electron microscopy (DPC STEM) is a powerful technique for directly visualizing electromagnetic fields inside materials at high spatial resolution. Electric field observation within ferroelectric materials is potentially possible by DPC STEM, but concomitant diffraction contrast hinders the quantitative electric field evaluation. Diffraction contrast is basically caused by the diffraction-condition variation inside a field of view, but in the case of ferroelectric materials, the diffraction conditions can also change with respect to the polarization orientations. To quantitatively observe electric field distribution inside ferroelectric domains, the formation mechanism of diffraction contrast should be clarified in detail. In this study, we systematically simulated diffraction contrast of ferroelectric domains in DPC STEM images based on the dynamical diffraction theory, and clarify the issues for quantitatively observing electric fields inside ferroelectric domains. Furthermore, we conducted experimental DPC STEM observations for a ferroelectric material to confirm the influence of diffraction contrast predicted by the simulations.
差分相衬扫描透射电子显微镜（DPC STEM）是一种强大的技术，能够以高空间分辨率直接观察材料内部的电磁场。利用DPC STEM有可能在铁电材料中观察电场，但伴随的衍射衬度会妨碍电场的定量评估。衍射衬度基本上是由视场内衍射条件的变化引起的，但对于铁电材料而言，衍射条件也会随极化方向而改变。为了定量观察铁电畴内部的电场分布，需要详细阐明衍射衬度的形成机制。在本研究中，我们基于动力学衍射理论系统地模拟了DPC STEM图像中铁电畴的衍射衬度，并阐明了定量观察铁电畴内部电场时存在的问题。此外，我们对一种铁电材料进行了DPC STEM实验观察，以证实模拟预测的衍射衬度的影响。
