ONE Lab at Dept. of Physics, Sogang Univ.
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Our group investigates various functionalities of oxide thin films—such as ferroelectricity, flexoelectricity, and electronic/ionic transport—primarily using scanning probe microscopy (SPM). SPM is a powerful tool for studying phenomena at the nanoscale, as illustrated in the figure below.
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In particular, we are highly interested in the electromechanical responses of oxide thin films, including ferroelectricity, flexoelectricity, piezoelectricity, and electrochemical strain. We have extensively investigated ferroelectric thin films such as BaTiO3, Pb(Zr,Ti)O3, BiFeO3, and HfO2-based materials. Using various SPM techniques—primarily piezoresponse force microscopy (PFM)—we have studied ferroelectricity and associated domain properties. We are also exploring new SPM methods for probing ferroelectricity, including band excitation PFM and contact Kelvin probe force microscopy (cKPFM).
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We are also highly interested in nanoscale electronic and/or ionic transport phenomena in oxide thin films. Our investigations have encompassed ferroelectric thin films, solid oxide fuel cell (SOFC) materials (e.g., Sm:CeO2–SrTiO3 vertical heterostructures), and metal–insulator transition (MIT) materials (e.g., VO2). By employing various SPM techniques—primarily conductive atomic force microscopy (cAFM)—we have studied local conduction behaviors and elucidated their underlying mechanisms.
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In addition to conventional oxide-based systems, our research has expanded to low-dimensional hybrid materials such as two-dimensional (2D) halide perovskites. These layered materials offer enhanced structural flexibility and exhibit unique ferroelectric and optoelectronic properties. We have investigated nanoscale ferroelectric domains and their temperature-dependent evolution using advanced PFM techniques. Our study has revealed spatially resolved ferroelectric-to-paraelectric phase transitions and provided insights into their underlying mechanisms.
