Department of Physics,
Kyungpook National University
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콜로퀴움/세미나 자료실

(콜로퀴움) Emergent Functionalities on Transition Metal Oxide Heterostructures

  • 관리자
  • 2021-09-27 09:04
  • hit 83
2021년 9월29일(수) 오후 5시
제1과학관 120호
강경태 교수(경북대학교 물리학과)

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학생들의 많은 참여 바랍니다.

Designing transition metal oxide heterostructure is like ‘a LEGO brick play’  using atom pieces. One with many atomic LEGO pieces, including oxygen, can construct an oxide heterostructure on her/his hands. Due to diverse parameters such as transition metals of multivalence, epitaxial strain, and      stoichiometry, the oxide heterostructure has shown intriguing properties for  fundamental physics on top of applications. Significantly, the development  of the growth methodology of pulsed laser deposition (PLD) helps us precisely  engineer the nano-to-macro structure of oxide heterostructures.

Here, we introduce a variety of emergent functionalities in transition metal   oxide heterostructure. First, we report a nano-scale real-time observation of oxygen vacancy-driven topotactic phase transformation from the perovskite  SrFeO3 to brownmillierite SrFeO2.5. Topotactic phase transformation provides avenues for understanding and tailoring important functionalities across    multiple disciplines, including electrochemical activities, structural symmetry modification, and metal-to-insulator transition. However, direct real-time atomic-scale imaging has not been possible so far. Oxygen vacancy formation, migration, and order during the PV-to-BM transformation were studied through quantitative analyses of oxygen intensity and cation sublattice movement at the atomic scale. Our real-time high-resolution transmission electron microscopy (HRTEM) movie, in conjunction with density functional theory(DFT) calculation, unravels the oxygen migration pathway responsible for the collective lattice dynamic motion.

Second, we investigated the emergent functionalities in the exotic structure  of freestanding oxide membranes, in which room-temperature ferroelectrici-ty or ferromagnetism arises. BaTiO3/La0.7Sr0.3MnO3 bilayer and CoFe2O4 membranes fabricated by using pulsed laser epitaxy have been utilized to look into the effect of various strain environments, from non-strained to massive bending, on the emergent ferroelectricity and ferromagnetism.