Effects of Electron channeling in HAADF-STEM intensity in La2CuSnO6
Effects of Electron channeling in HAADF-STEM intensity in La2CuSnO6
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DOI：
10.1016/j.ultramic.2009.01.004
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发表时间：
2009-03-01
期刊：
影响因子：
2.2
通讯作者：
Isoda, S.
中科院分区：
文献类型：
--
作者：
Haruta, M.;Kurata, H.;Isoda, S.
利用高角度环形暗场扫描透射电子显微镜（HAADF-STEM）进行原子分辨率成像，可以直接分析材料的原子结构。这种技术提供了与组成元素原子序数不一致的z -对比。在本工作中，观察到独特的对比，使得直观地解释双钙钛矿氧化物La2CuSnO6中的HAADF-STEM图像变得困难。多层模拟证实，这是电子的通道过程与德拜-沃勒因子的影响相结合的结果。这是因为在La2CuSnO6晶体中，两个独立的Sn原子和四个独立的La原子具有不同的Debye-Waller因子，并且La柱由小间距的对柱组成，而Sn原子呈直线排列。在此基础上，通过多层模拟检测了图像的对比度，将两个原子La柱在投影平面上分离，并通过多层模拟显示为一列对比度。结果表明，除了极薄样品外，HAADF强度并没有随着柱间距的增加而不断降低，这可以通过电子通道过程的特定变化来解释。爱思唯尔B.V.版权所有
Atomic resolution imaging using the high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) can be applied to analyze the atomic structures of materials directly. This technique provides incoherent Z-contrast with the atomic number of the constituent elements. In the present work, unique contrasts that make intuitively interpreting the HAADF-STEM image in double perovskite oxide La2CuSnO6 difficult were observed. Multislice simulation confirmed that this occurred as an effect of the channeling process of electrons in combination with the effect of Debye-Waller factors. This was confirmed because in the La2CuSnO6 crystal, two independent Sn atoms and four independent La atoms in the unit cell had different Debye-Waller factors, and the La columns consisted of pairs of columns with a small separation, whereas the Sn atoms were arranged straight. Furthermore, the image contrast was examined by mutislice simulation, and two atomic La columns were separated in a projected plane and appeared as one column contrast using multislice simulation. As a result, the HAADF intensity did not decrease constantly with the increase in column separation, with the exception of a very thin sample, which could be interpreted by the specific change in the electron-channeling process. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.