PPT《2010年第26期》

2010年第26期 时间:12月9日(星期四)15:00-16:40地点:北京大学物理大楼中212教室 Characterization at picometres precision of structure and properties of ferroelectric oxides Photograph by Xiaodong Hu 贾春林 教授德国于利希研究中心(Forschungszentrum Jülich GmbH)研究员西安交通大学国际电介质研究中心教授 联系人: 俞大鹏教授 email:dpyu@pku.

edu.cn Abstract: Epitaxial thin films of ferroelectric oxides have attracted increasingly intensive research both for fundamental and application issues. The physical properties of these film systems depend strongly on the particular microstructure and configuration of lattice defects. By means of an aberration corrector in a high-resolution transmission electron microscope the value of the spherical aberration CS can be tuned to negative values resulting in a novel imaging technique: The negative CS imaging (NCSI) technique. The images obtained with the NCSI technique are superior to positive CS images in the magnitude of the contrast and the image intensity of atom columns. The image signal obtained with the NCSI technique is significantly more robust against noise, resulting in measurement of atomic positions with a precision of a few picometres. In this talk, we present the results of a study using NCSI technique of the epitaxial thin-film system of PbZr0.2Ti0.8O3. The positions of all the atomic species are measured, unit cell by unit cell, with a precision of a few picometres. On this basis the relative ion displacement and the electric dipole moment for the individual unit cells are calculated. The resulting dipole moments depict the details of polarization domains, domain walls, as well as the local variation of spontaneous polarization at defect areas. 北京大学物理学院凝聚态物理与材料物理所 http://www.phy.pku.edu.cn/events/icmp10f.xml 凝聚态物理-北京大学论坛 贾春林 :基于球差校正高分辨率透射电子显微镜的球差值可调性,开发了一新的高分辨成像模式-负球差成像技术,并应用于材料结构及缺陷的原子尺度研究.相对于传统的正球差成像模式,负球差成像的显著优越性是可产生更高的像衬度,增强高分辨电子显微像的信号强度,从而提高定量分析的精度.借助于负球差成像技术,在原子尺度定量地表征了BaTiO3(111)孪晶界面中的氧缺陷.用定量高分辨电子显微术对铁电氧化物薄膜中的界面、缺陷及其对纳米及亚纳米区域铁电性能的影响进行了原子尺度地研究分析,实现了测量表征单胞铁电偶极矩及纳米区铁电性能.