Li Jun, Cheng Shaobo, Wu Lijun, Tao Jing, Zhu Yimei
Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, NY 11973, USA.
Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, NY 11973, USA; Stony Brook University, Stony Brook, NY 11794, USA.
Ultramicroscopy. 2018 Nov;194:167-174. doi: 10.1016/j.ultramic.2018.07.011. Epub 2018 Jul 30.
Geometric phase analysis (GPA) is a useful method to map strain distribution in atomically resolved scanning/transmission electron microscopy (S/TEM) images. Nevertheless, the inevitable periodic jitter of electron probe in STEM along the scanning direction due to the interference of electric power supply, including grounding, can give rise to major artifacts, as evidenced by the appearance of satellite spots surrounding all main peaks in the power spectrum of the images. Here we reveal the origin of the image artifacts related to the probe jitter by mapping the image distortion component ε using the GPA algorithm. The effect is verified by introducing a periodic displacement field to a STEM image simulated from a perfect crystal structure, and the calculated ε maps show very good agreement with the experimental observations. Based on the quantitative analysis of the images distortion, we propose and test a feasible strategy to eliminate the effect of probe jitter from STEM images. Successful examples illustrate that the approach can help improve the accuracy in quantification of STEM images.
几何相位分析（GPA）是一种用于在原子分辨扫描/透射电子显微镜（S/TEM）图像中绘制应变分布的有用方法。然而，由于包括接地在内的电源干扰，扫描透射电子显微镜（STEM）中电子探针沿扫描方向不可避免的周期性抖动会产生主要伪像，图像功率谱中所有主峰周围出现卫星斑点就证明了这一点。在这里，我们通过使用GPA算法绘制图像失真分量ε来揭示与探针抖动相关的图像伪像的起源。通过将周期性位移场引入从完美晶体结构模拟的STEM图像中来验证这种效应，计算得到的ε图与实验观察结果非常吻合。基于对图像失真的定量分析，我们提出并测试了一种可行的策略来消除STEM图像中探针抖动的影响。成功的例子表明，该方法有助于提高STEM图像量化的准确性。
