报 告 一: Atomic Scale Visualization of Light Elements in Advanced Functional Oxide Materials

　　主讲嘉宾：黄荣 教授（华东师范大学）

　　报 告 二: 铁电薄膜中的畴翻转动力学和极化屏蔽机制的电子显微学研究

　　主讲嘉宾：高鹏 研究员（北京大学）

　　报告时间： 5月12日（周五）上午9:00-11:30

　　报告地点：李薰楼468会议室

　　报告一简介：

　　Light elements, such as Li and O, are the key component in many advanced materials like cathode materials for lithium ion battery and transition metal oxides for ferroelectric applications. Thus the local structures of light elements play a very important role on their physical properties and the electrochemical performance of lithium ion batteries. However, visualization of the light elements like Li and O are very difficult by electron microscopy because of their weak scatter capability to the electron beam.

　　With the development of spherical aberration corrector in the beginning of this century, scanning transmission electron microscope (STEM) equipped with an annular dark-field (ADF) detector and electron energy-loss spectrometer (EELS) becomes a very powerful tool to obtain useful structural and chemical information with atomic resolution. Very recently, annular bright-field (ABF) STEM imaging has been successfully used to image columns of both light and heavy elements simultaneously with good signal-to-noise ratio. This is a very promising technique because of its sensitivity to light elements and the robustness of the interpretation of direct images for a large range of sample thicknesses.

　　In this talk, we demonstrate some examples on the atomic-level imaging of light elements in various advanced oxide materials using the-state-of-the-art Cs-corrected STEM techniques:

　　(1) Direct observation of Li ions in LiMn2O4 and LiCoO2 cathode materials in real-space and real-time by using the ABF-STEM imaging technique.

　　(2) The preferential site occupancy of Mn in γ–Ga2O3 and the dedicate control of Mn valency.

　　(3) The Polarization pinning and relaxation at coherent BiFeO3/LaAlO3 interfaces.

　　报告一主讲嘉宾简介:

   Professor Rong Huang is a professor of the Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University (ECNU). He is also a guest researcher of the Japan Fine Ceramics Center (JFCC).

　　Prof. Huang received the B.S. degree in materials science and engineering from the Chongqing University, Chongqing, China in 1999, and the Ph.D. degree in materials physics and chemistry from the Shanghai Institute of Ceramics, Chinese Academy of Science, Shanghai, China, in 2005. He was a Postdoctoral Researcher in Kyoto University from April 2005 to March 2007 and at the Japan Fine Ceramics Center from April 2007 to March 2009. Since April 2009, he has been with the Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University. His current research interests are the microstructure characterization of various ceramic materials, cathode materials of lithium ion batteries and functional oxide thin films by the state-of-the-art spherical aberration corrected scanning transmission electron microscopy (Cs-corrected STEM) techniques to reveal the synthesis-microstructure-property relationships and the related physical mechanisms.

　　报告二简介：

　　Ferroelectrics thin films have numerous important applications including high-density and non-volatile memories, acoustic devices, and sensors. We study the domain switching dynamics and polarization charge screening mechanisms in ferroelectric thin films by using electron microscopy techniques. (1) In situ biasing and indentation TEM techniques are used to track the ferroelectric domain nucleation, domain wall relaxation, structural defects pinning, and ferroelastic domain wall mediated ferroelectric switching. (2) Quantitative annular bright field imaging is used to measure the structural relaxation and polarization distribution at the surface, interface, and defects with picometer precision.

　　报告二主讲嘉宾简介：

　　高鹏，北京大学物理学院研究员/助理教授，博士生导师，北京大学电子显微镜实验室副主任。2005年在中国科学技术大学获得物理学学士学位，2010年在中国科学院物理研究所获得凝聚态物理学博士学位，2010-2015年间在美国密歇根大学、美国布鲁克海文国家实验室、日本东京大学从事博士后研究工作。从研究生期间开始一直从事透射电子显微学相关的研究，主要包括：（1） 晶体材料的表面、界面、缺陷结构；（2）外场下的结构相变；（3）固态离子迁移动力学过程等。共发表论文48篇，累计引用1300多次，其中包括10篇Nature子刊和1篇Science。曾获中科院宝洁奖、优秀毕业生奖，中科院物理所所长优秀奖、表彰奖等，曾入选日本振兴学会（JSPS）外国人特别研究员。