de Graaf Sytze, Ahmadi Majid, Lazić Ivan, Bosch Eric G T, Kooi Bart J
Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
Thermo Fisher Scientific, Achtseweg Noord 5, 5651 GG Eindhoven, The Netherlands.
Nanoscale. 2021 Dec 16;13(48):20683-20691. doi: 10.1039/d1nr06614e.
Scanning transmission electron microscopy (STEM) is the most widespread adopted tool for atomic scale characterization of two-dimensional (2D) materials. However, damage free imaging of 2D materials with electrons has remained problematic even with powerful low-voltage 60 kV-microscopes. An additional challenge is the observation of light elements in combination with heavy elements, particularly when recording fast dynamical phenomena. Here, we demonstrate that 2D WS suffers from electron radiation damage during 30 kV-STEM imaging, and we capture beam-induced defect dynamics in real-time by atomic electrostatic potential imaging using integrated differential phase contrast (iDPC)-STEM. The fast imaging of atomic electrostatic potentials with iDPC-STEM reveals the presence and motion of single sulfur atoms near defects and edges in WS that are otherwise invisible at the same imaging dose at 30 kV with conventional annular dark-field STEM, and has a vast speed and data processing advantage over electron detector camera based STEM techniques like electron ptychography.
扫描透射电子显微镜（STEM）是用于二维（2D）材料原子尺度表征的应用最为广泛的工具。然而，即便使用强大的60 kV低电压显微镜，对二维材料进行无损伤电子成像仍然存在问题。另一个挑战是对轻元素与重元素组合的观察，尤其是在记录快速动态现象时。在此，我们证明二维WS在30 kV-STEM成像过程中会遭受电子辐射损伤，并且我们通过使用集成差分相衬（iDPC）-STEM的原子静电势成像实时捕捉了束流诱导的缺陷动力学。iDPC-STEM对原子静电势的快速成像揭示了WS中缺陷和边缘附近单个硫原子的存在与运动，而在30 kV下以相同成像剂量使用传统环形暗场STEM时这些原子是不可见的，并且与基于电子探测器相机的STEM技术（如电子叠层成像）相比，iDPC-STEM具有巨大的速度和数据处理优势。
