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报告题目：From Atomic Structure to Properties of Oxides -Applications of Quantitative HR(S)TEM

报  告 人： 贾春林 教授（Jia-Lab for Interface and Atomic Structure, Xi"an Jiaotong University, and Ernst Ruska Center for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich, D-52425 Jülich, Germany）

报告时间：2018年4月11日（星期三），下午4:30

报告地点：威廉希尔六层学术报告厅（致知楼3623）

报告摘要：

Functional oxides with their exceptional variety of physical properties are important part of the material basis for future multifunctional devices. The physical properties of these oxides depend strongly on the particular crystal structure and configuration of lattice defects that are unavoidably occur in the crystal matrix. In particular, the interfaces and domain walls (or boundaries) of functional oxides exhibit novel properties differing from the bulk matrix, such as conductivity, ferromagnetism and photovoltaic properties [1]. These novel properties have attracted considerable interest of research on the underlying physics with respect to structural origin and their potential application in nano-electronics.

Aberration-corrected high-resolution (scanning) transmission electron microscopy (HR(S)TEM) has proven to be a powerful tool for materials research [2]. For crystalline materials quantitative HR(S)TEM can be used for determining the position of atomic columns with a precision of a few picometers and the chemical occupancy in atomic columns with a precision of a few atomic percent. With quantitative evaluation of image contrast of a thin crystal, the number of atoms within the atomic columns parallel to the viewing direction has been determined [3].

In the present lecture, quantitative HR(S)TEM and examples for its applications to studying oxide materials are presented. Employing quantitative HR(S)TEM, domain walls in ferroelectric Pb(ZrTi)O₃ thin films and topological structures and defects in multilayer films of SrTiO₃/PbTiO₃ are studied [4-6]. We measure with picometer precision the positions and relative displacements of the atoms. The precisely measured displacements of atoms are used to determine the modulus and the direction of the electric dipole moments unit cell by unit cell, which reveals the domain walls and topological structures and defects. 

     1.   J. Mannhart and D. G. Schlom, Science 327, 1607 (2010).

     2.   C.L. Jia, M. Lentzen, K. Urban, Science 299, 870 (2003).

     3.   C.L. Jia et al., Nat. Mater. 13, 1044 (2014).

     4.   C.L. Jia et al., Nat. Mater. 7, 57 (2008).

     5.   C.L. Jia et al., Science 331, 1421 (2011).

     6.   L. Lu et al., Phys. Rev. Letts. (2018) in press. 

报告人简介：

贾春林，国际知名电镜专家，西安交通大学教授、贾春林科学家工作室首席科学家、德国于利希研究中心资深研究员，于1993 获德国亚琛工大博士学位。在氧化物材料及畴界面的亚纳米结构缺陷与性能，以及定量高分辨透射电子显微学研究领域做出了具有重要影响力的工作。基于球差校正高分辨透射电子显微镜中的球差值可调性，开发了一新的高分辨透射电子成像模式:负球差成像技术，并应用于氧化物材料结构及缺陷的原子尺度研究。基于负球差成像技术，对铁电氧化物的畴界面及缺陷进行了真正原子尺度的开创性研究。借助于定量高分辨率透射电子显微学，对导致铁电氧化物自发极化的离子位移进行了测量，在原子尺度上实现对晶体单胞电偶极矩的定量。特别是对畴界面、晶格缺陷对纳米及亚纳米区域铁电性能的影响进行了原子尺度地测量分析，实现了用电子显微技术在单胞尺度上表征了铁电材料的宏观性能。发表论文180余篇，多篇发表在具有重要影响力的杂志上（Science、Nature Materials、Physical Review Letters等 ）；荣获郭可信杰出科学家奖（2004）、国际显微学联合会(IFSM) Hatsujiro Hashimoto Medal (2014)、中国电镜学会钱临照奖（2014）。

 代表性工作

          [1]     C. L. Jia, S. B. Mi, J. Barthel, D. W. Wang, R. E. Dunin-Borkowski, K. W. Urban, and A. Thust, “Determination of the 3D shape of a nanoscalecrystal with atomic resolution from a single image”. Nature Materials 13, 1044 (2014).

          [2]     C. L. Jia, K. Urban, M. Alexe, D. Hesse and I. Vrejoiu, “Direct observation of continuous electric dipole rotation in flux-closure domains in ferroelectric Pb(Zr,Ti)O₃”. Science, 331: 1421, 2011.

          [3]     A.H. Heuer, C. L. Jia, and K.P.D. Lagerl?f, The core structure of basal dislocations in deformed sapphire (α-Al₂O₃), Science 330, 1227 (2010).

          [4]     C. L. Jia, S.B. Mi, K. Urban, I. Vrejoiu, M. Alexe and D. Hesse, “Effect of a single dislocation in a heterostructure layer on the local polarization of a ferroelectric layer”. Phys. Rev. Lett. 102, 117601 (2009).

          [5]     C. L. Jia, S.B. Mi, K. Urban, I. Vrejoiu, M. Alexe and D. Hesse, “Atomic-scale study of electric dipoles near charged and uncharged domain walls in ferroelectric films”. Nature Materials 7, 57 (2008).

          [6]     C. L. Jia, V. Nagarajan, J. Q. He, L. Houben, T. Zhao, R. Ramesh, K. Urban and R. Waser, “Unit-cell scale mapping of ferroelectricity and tetragonality in epitaxial ultrathin ferroelectric films”. Nature Materials 6, 64 (2007).

          [7]     C. L. Jia, A. Thust, K. Urban, Atomic-scale analysis of the oxygen configuration at a SrTiO₃ dislocation core”. Phys. Rev. Lett. 95, 225506 (2005).

          [8]     C. L. Jia and K. Urban, “Atomic-resolution measurement of oxygen concentration in oxide materials”. Science 303, 2001 (2004).

          [9]     C. L. Jia, M. Lentzen and K. Urban, “Atomic-resolution imaging of oxygen in perovskite ceramics”. Science 299, 870 (2003).

          [10]  C. L. Jia and A. Thust, Investigation of atomic displacements at a ?3 {111} twin boundary in BaTiO₃ by means of phase-retrieval electron microscopy, Phys. Rev. Lett. 82, 5052 (1999).

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2018年4月3日