Sang Xiahan, LeBeau James M
Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27695-7907, USA.
Ultramicroscopy. 2014 Mar;138:28-35. doi: 10.1016/j.ultramic.2013.12.004. Epub 2013 Dec 31.
We report the development of revolving scanning transmission electron microscopy--RevSTEM--a technique that enables characterization and removal of sample drift distortion from atomic resolution images without the need for a priori crystal structure information. To measure and correct the distortion, we acquire an image series while rotating the scan coordinate system between successive frames. Through theory and experiment, we show that the revolving image series captures the information necessary to analyze sample drift rate and direction. At atomic resolution, we quantify the image distortion using the projective standard deviation, a rapid, real-space method to directly measure lattice vector angles. By fitting these angles to a physical model, we show that the refined drift parameters provide the input needed to correct distortion across the series. We demonstrate that RevSTEM simultaneously removes the need for a priori structure information to correct distortion, leads to a dramatically improved signal-to-noise ratio, and enables picometer precision and accuracy regardless of drift rate.
我们报告了旋转扫描透射电子显微镜（RevSTEM）的开发，这是一种无需先验晶体结构信息就能从原子分辨率图像中表征并消除样品漂移畸变的技术。为了测量和校正畸变，我们在连续帧之间旋转扫描坐标系时获取图像序列。通过理论和实验，我们表明旋转图像序列捕获了分析样品漂移速率和方向所需的信息。在原子分辨率下，我们使用投影标准偏差来量化图像畸变，这是一种直接测量晶格矢量角度的快速实空间方法。通过将这些角度拟合到物理模型，我们表明优化后的漂移参数提供了校正整个序列畸变所需的输入。我们证明，RevSTEM同时消除了校正畸变对先验结构信息的需求，显著提高了信噪比，并且无论漂移速率如何都能实现皮米级的精度和准确度。
