Picometer-scale atom position analysis in annular bright-field STEM imaging
Picometer-scale atom position analysis in annular bright-field STEM imaging
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环形明场 STEM 成像中的皮米级原子位置分析
DOI：
10.1016/j.ultramic.2017.09.001
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发表时间：
2018-01-01
期刊：
影响因子：
2.2
通讯作者：
Ikuhara, Yuichi
中科院分区：
文献类型：
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作者：
Gao, Peng;Kumamoto, Akihito;Ikuhara, Yuichi
在环形光场扫描透射电镜（ABF-STEM）中，通过实验与模拟相结合的方法，研究了试样不倾斜对局部结构皮米尺度测量的影响。提出了一种相对距离测量方法，将倾斜效应与扫描噪声和样品漂移引起的图像畸变分离开来。我们发现，在典型的实验条件下，25 nm厚的SrTiO3沿[001]的小试样倾斜（类似于6 mrad）会导致ABF图像中O和Sr/TiO柱之间11.9 pm的人工位移，这是扫描噪声和样品漂移引起的图像畸变（类似于3.2 pm）的3倍以上，表明倾斜效应可能是ABF图像定量分析的主导因素。伪影取决于晶体的不倾斜角度、试样厚度、离焦、会聚角和未校正的像差。我们的研究为在实验操作和数据分析中检测和纠正倾斜效应提供了有益的见解，以提取真实的结构信息，避免对原子结构和氧八面体畸变/移位等性质的错误解释。(C) 2017 Elsevier B.V.版权所有
We study the effects of specimen mistilt on the picometer-scale measurement of local structure by combing experiment and simulation in annular bright-field scanning transmission electron microscopy (ABF-STEM). A relative distance measurement method is proposed to separate the tilt effects from the scan noise and sample drift induced image distortion. We find that under a typical experimental condition a small specimen tilt (similar to 6 mrad) in 25 nm thick SrTiO3 along [ 001] causes 11.9 pm artificial displacement between O and Sr/TiO columns in ABF image, which is more than 3 times of scan noise and sample drift induced image distortion similar to 3.2 pm, suggesting the tilt effect could be dominant for the quantitative analysis of ABF images. The artifact depends on the crystal mistilt angle, specimen thickness, defocus, convergence angle and uncorrected aberration. Our study provides useful insights into detecting and correcting tilt effects during both experiment operation and data analysis to extract the real structure information and avoid mis-interpretations of atomic structure as well as the properties such as oxygen octahedral distortion/shift. (C) 2017 Elsevier B.V. All rights reserved.