아래와 같이 세미나를 개최하오니 많은 참석 부탁드립니다.
- Speaker : Prof. Sang Ho Oh (Department of Energy Engineering, KENTECH Institute for Energy Materials and Devices, Korea Institute of
- Date : 2024.01.26(Fri) 3:00pm
- Place : E6-2 #1323
- Title : "In-situ 4D-STEM studies on surface reconstruction and polarization switching of perovskite oxides"
- Abstract :
4D STEM is an emerging technique in electron microscopy, enabling the acquisition of convergent electron beam diffraction (CBED) patterns in every pixels in STEM mode. This technique is versatile and finds many useful applications in materials science, where conventional TEM and STEM techniques are unable to characterize. For example, the quantitative interpretation of the CBED pattern can provide detailed information on the crystal symmetry and atomic positions at an Å level, allowing the precise determination of lattice strain and atomic displacement. 4D STEM data, acquired at an optimized condition for ptychography and treated by iterative phase reconstruction algorithms, can be used for atomic-scale potential and charge density mapping. Further, the ptychography of 4D STEM can achieve a good depth resolution in the range of ~2-5 nm once the multislice wave propagation is incorporated into the iterative phase reconstruction process. If all these capabilities of 4D STEM is combined with in-situ TEM experiments, such as heating and electrical biasing, tremendous breakthrough can made in various fields of materials science and solid-state physics. In this seminar, some of our recent (unpublished) works on the surface reconstruction of SrTiO3 (001) at high temperatures and the mapping of field-induced polarization switching of relaxor ferroelectric Ba0.5Sr0.5TiO3 thin films will be presented.