Educations 

• 2009 - 2014 University of Michigan (Ph.D. in Physics)
• 2003 - 2009 Seoul National University (B.S. in Physics)

Research Overview

Atoms are the basic building blocks of matter. The physical properties of most materials are strongly influenced by the 3D arrangement of individual atoms. To understand material properties and functionality at the most fundamental level, it is essential to precisely determine their 3D atomic arrangement. Crystallography has long been the method of choice for 3D atomic structure determination from crystalline samples. However, perfect crystals are rare in nature. Most real materials contain disordered structures: defects, grain boundaries, stacking faults, and dislocations. Moreover, these non-crystalline structures can evolve into different structures during phase transition, but their atomic-scale dynamics is poorly understood yet due to the lack of proper tools with the capability of measuring the non-crystalline structures.

Our work goes beyond crystallography—allowing 3D atomic structure determination of complex materials without crystallographic assumption. Utilizing state-of-art aberration corrected electron microscopes and powerful reconstruction algorithms, atomic electron tomography (AET) can now reveal full 3D atomic structures of various nanomaterials and their dynamics. Moreover, excellent brilliance and coherence of 3rd generation synchrotron x-ray sources allowed the detection of crystal truncation rods (CTRs) arises from materials surfaces and interfaces. Surface X-Ray Diffraction (SXRD) can determine the atomic structure of the surface/interface at sub-picometer regime by sampling the full 3D Fourier space of the surface/interface system.

Our group works at the frontiers of the multi-dimensonal atomic structural research, and the scientific importance and impact of these findings are reflected in our publication records, which have been prominently featured in premier journals and news articles (please visit our Publications and News pages). Further developing the powerful and unique tools we have, our group seeks to measure the full 3D atomic structures of materials and their dynamics, which have not been able to be observed before. Ultimately, we aim to address important unsolved problems in condensed matter physics and materials science, including the atomic scale dynamics in nucleation & phase transition, structural formation phase diagram of amorphous materials, high-entropy alloys, underlying physics on the Verwey transition of magnetite, and many more!

LAB

Multi-Dimensional Atomic Imaging Lab