Scanning transmission electron microscopy (STEM) allows detailed atomic displacements in ferroelectrics to be studied. Although the interpretation of the displacements is straightforward for single-domain structures, it is complicated when multiple domains are present in the direction of the electron beam. In the present study, we simulated STEM images to obtain insight into the observed ionic displacements for multi-domain structures in a prototypic ferroelectric, barium titanate. We found that the observed displacements can vary depending on the domain configuration, domain thicknesses, and the defocus of the electron probes. Observed displacement behaviors were dominantly contributed by the upper domain when focusing the electron beam on the upper surface of samples, whereas interpretation of the behaviors became complex when the electron probe was focused on their inside. These results suggest that comparison of experimental observations with simulations is necessary to better understand the displacement behavior.
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