Institute of Engineering Innovation, The University of Tokyo , 2-11-16, Yayoi, Bunkyo-ku, Tokyo 113-8656, Japan.
Department of Materials Science and Engineering, Drexel University , Philadelphia, Pennsylvania 19104, United States.
ACS Nano. 2015 Aug 25;9(8):8412-9. doi: 10.1021/acsnano.5b03232. Epub 2015 Jul 29.
The rich functionalities in the ABO3 perovskite oxides originate, at least in part, from the ability of the corner-connected BO6 octahedral network to host a large variety of cations through distortions and rotations. Characterizing these rotations, which have significant impact on both fundamental aspects of materials behavior and possible applications, remains a major challenge at heterointerfaces. In this work, we have developed a unique method to investigate BO6 rotation patterns in complex oxides ABO3 with unit cell resolution at heterointerfaces, where novel properties often emerge. Our method involves column shape analysis in ABF-STEM images of the ABO3 heterointerfaces taken in specific orientations. The rotating phase of BO6 octahedra can be identified for all three spatial dimensions without the need of case-by-case simulation. In several common rotation systems, quantitative measurements of all three rotation angles are now possible. Using this method, we examined interfaces between perovskites with distinct tilt systems as well as interfaces between tilted and untilted perovskites, identifying an unusual coupling behavior at the CaTiO3/LSAT interface. We believe this method will significantly improve our knowledge of complex oxide heterointerfaces.
ABO3 钙钛矿氧化物丰富的功能至少部分源自于通过变形和旋转，顶角相连的 BO6 八面体网络能够容纳大量不同阳离子这一能力。在异质界面处，对这些旋转进行分析，这对材料行为的基本方面和可能的应用都有重大影响，但仍然是一个主要挑战。在这项工作中，我们开发了一种独特的方法，能够以单元晶胞分辨率研究异质界面处复杂氧化物 ABO3 中的 BO6 旋转模式，因为在这些异质界面处经常会出现新的性质。我们的方法涉及以特定取向在 ABF-STEM 图像中对 ABO3 异质界面进行柱状形状分析。无需逐个进行模拟，就可以识别出 BO6 八面体的旋转相在所有三个空间维度上的情况。现在可以对所有三个旋转角度进行定量测量，在几种常见的旋转系统中。使用这种方法，我们研究了不同倾斜系统钙钛矿之间的界面以及倾斜和未倾斜钙钛矿之间的界面，在 CaTiO3/LSAT 界面处发现了一种不寻常的耦合行为。我们相信这种方法将极大地提高我们对复杂氧化物异质界面的认识。
