Seminar & Colloquium
[세미나: 9월 8일(금), 오후 4시 30분] Prof. Xiaoqing Pan, University of California
Title
Probing the Emergent Properties and Dynamics of Interfaces by Electron Microscopy
Speaker
Prof. Xiaoqing Pan, University of California
Bio
Xiaoqing Pan is the Henry Samueli Endowed Chair in Engineering, professor of materials science and engineering, and professor of physics and astronomy. He is also the inaugural director of the Irvine Materials Research Institute (IMRI), and founding director of the Center for Complex Active Materials – an NSF MRSEC. Pan is an internationally recognized materials scientist and electron microscopy expert due to his pioneering development and applications of novel transmission electron microscopy (TEM) methods for probing the atomic scale structure, properties and dynamic behaviors of materials. His work has led to the discoveries of new materials and novel functionalities. Pan has received the NSF CAREER Award and the Chinese NSF’s Outstanding Young Investigator Award. He is an elected fellow of the American Ceramic Society, American Physical Society, Microscopy Society of America, and the Materials Research Society. He has published over 400 peer-reviewed scientific papers in high impact journals.
| Date | Friday, September 8th, 2023
| Time | 16:30 ~
| Venue | 33동 328호
[Abstract]
The advancements in aberration correctors, pixelated direct electron detectors, and monochromators represent significant milestones in the development of transmission electron microscopy (TEM). These innovations have enabled the imaging of materials' structure, chemistry, and functional properties at the atomic scale. In this talk, I will introduce a novel four-dimensional scanning transmission electron microscopy (4D STEM) method. This method facilitates the imaging of local polarization, electric fields, and charge density in multiferroic oxide nanostructures with sub-angstrom resolution. I will demonstrate how polarization at ferroelectric/insulator interfaces influences functional properties, such as strain, bonding, electric field and charge distributions. Through the combination of 4D STEM and scanning probe microscopy, we have observed unique skyrmion-like polar nanodomains in freestanding PbTiO3/SrTiO3 bilayers transferred onto silicon. These nanodomains can be toggled between states by an applied electric field, leading to substantial alterations in their resistive behaviors. In the subsequent part of the presentation, I will introduce innovative space- and angle-resolved electron energy-loss spectroscopy (EELS) methods. These techniques enable us to uncover novel vibrational modes and emergent phonons at single defects or interfaces in crystalline materials. We can map changes in phonon momentum, revealing the direction of phonon propagation and, consequently, heat flow at the nanoscale. Utilizing this technique, we found that sharp interfaces between different materials exhibit markedly superior heat conduction compared to gradual, diffuse ones. These novel methodologies hold valuable potential for studying real nanodevices and enhancing our comprehension of charge distribution and heat dissipation in nanostructures and interfaces.
| Host | 강기석 교수(02-880-7088)