报 告 人： 付学文 博士

报告题目： 四维电子显微术及其在研究纳米材料超快结构和能量载流子动力学中的应用

时    间： 2018  年  4 月 11 日（星期 三 ）下午3：30

地    点： 材A307

报告人简介：

美国布鲁克海文国家实验室助理科学家（合作导师，朱溢眉教授）。本科及博士分别毕业于北京师范大学（2009年）及北京大学（2014年，博士导师：俞大鹏院士）。博士毕业后加入加州理工学院的Ahmed Zewail教授（1999年诺贝尔化学奖得主）课题组从事四维电子显微术研究，期间率先发展了液相四维电镜技术，将四维电子显微术的动力学研究扩展到了液相。他于2017年6月作为助理科学家加入布鲁克海文国家实验室，从事基于原位球差透射电镜和超快电子显微术的动力学原理研究。付学文博士的研究领域包括对能源材料中超快结构、能量载流子动力学的四维电子显微术和超快光谱研究，以及基于原位球差电镜的纳米材料物理、化学性质研究。他已经发表了超过27篇论文，其中包括15篇以第一作者发表在Science，Science Advances，Advanced Materials，ACS Nano（4篇）等重要期刊上。

欢迎广大师生踊跃参加！

科技处    材料科学与工程学院

2018年4 月 9 日

报告摘要：

In the past decade, four-dimensional electron microscopy (4D-EM), which enables the direct observation of transient structures, morphologies and carrier transport of materials in real time and space, has attracted increasing interest to the research community due to its powerful capability in the interdisciplines of physics, chemistry, material science, and biology. In this talk, I will firstly give a brief introduction of the development of 4D-EM and the state-of-the-art of its applications in research. Then I will present the recent development of liquid-phase 4D transmission electron microscopy and its first application in imaging Brownian dynamics of nanoparticles in liquid on the nanometer-nanosecond time scale. Both the translational and rotational dynamics of individual nanoparticles were imaged in both diffusion and ballistic regimes, and a full transition from diffusive to superdiffusive, and further to ballistic rotation was revealed with increasing the asymmetry of the particles. This advanced liquid-phase 4D-EM opens up a promising possibility for future study of numerous physical, chemical and biological dynamical processes in native environments. After that, I will talked about the recent development of 4D Lorentz-phase imaging in 4D EM, and the latest study of magnetization dynamics and dynamical switching of magnetic vortex in ferromagnetic Permalloy disks. At last, I will show the 4D scanning electron microscopy study of ultrafast exciton transport dynamics in purposively strain-engineered ZnO micro/nanowires on the nanometer-picosecond time scale. This work demonstrates that strain gradient field could induced spatial change of the excitonic potential, and drive the excitons to drift fast along the strain gradient field, which possesses great potential for application in strain engineering enhanced semiconducting optoelectronic devices.