Department of Chemical Engineering and Materials Science and Department of Physics and Astronomy, University of California – Irvine, Irvine, CA
Xiaoqing Pan is a Professor and Henry Samueli Endowed Chair in Engineering, in Department of Chemical Engineering & Materials Science and Department of Physics & Astronomy at UC Irvine. He is also the inaugural Director of the Irvine Materials Research Institute (IMRI). Before moving to UC Irvine, Pan was the Richard F. and Eleanor A. Towner Professor of Engineering in Department of Materials Science and Engineering, and also Director of Electron Microbeam Analysis Laboratory at the University of Michigan, Ann Arbor. Pan's research interests center on understanding the atomic-scale structure-property relationships of advanced functional materials, including oxide electronics, ferroelectrics and multiferroics, and catalysts. He is recognized internationally for his work in electron microscopy, that has led to the discovery of new properties and novel functionalities in these technologically important materials. Pan has received awards including the National Science Foundation’s CAREER Award and the Chinese NSF’s Outstanding Young Investigator Award. Pan is a Fellow of the American Ceramic Society in 2011, a Fellow of the American Physical Society in 2013, and a Fellow of the Microscopy Society of America in 2014.
As advances in transmission electron microscopy (TEM) have enabled the determination of the three-dimensional structure and local properties of materials with the sub-angstrom resolution, the recent development of in situ TEM techniques allows one to follow the dynamic response of nanostructured materials to applied fields or to changes in atmosphere. In this talk, it will be shown that the polarization ordering and dynamic domain switching behaviors of ferroelectric/multiferroic thin films can be quantitatively determined by in situ TEM. It was found that the charged domain walls can be created or erased by applying a bias, and the resistance of the local film strongly depends on the characteristics of these charged domain walls. It will also be show that the surface monolayer of conducting oxide can induce a giant spontaneous polarization in ultrathin multiferroelectric films and that a peculiar rumpled nanodomain structure, which is in analog to morphotropic phase boundaries (MPB), is formed. Finally, it will be demonstrated that small defects in ferroelectric thin films can act as nano-building-blocks for the emergence of novel topological states of polarization ordering, namely, hedgehog/antihedgehog nanodomain arrays. The emergent polarization states such as hedgehog/antihedgehog and vortex/ antivortex topologies not only modify the local lattice symmetries and thus induce the coexistence of mixed-phases resembling the morphotropic phase boundary with high piezoelectricity, but also lead to flux-closure vortex structures. This finding clearly demonstrates a novel route to the enhanced functional properties in the material system with reduced dimension via engineering the surface boundary conditions.
邀 请 人： 白雪冬 （电话：8032 ）
联 系 人： 胡 颖 （电话：9361 ）