Wang Linhai, Liu Dongdong, Zhang Fan, Zhang Zhenyu, Cui Junfeng, Jia Zhenghao, Yu Zhibin, Lv Yiqiang, Liu Wei
Key Laboratory for Precision and Non-Traditional Machining Technology of Ministry of Education, Dalian University of Technology Dalian 116024 China
Division of Energy Research Resources, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences Dalian 116023 China
Nanoscale Adv. 2021 Mar 4;3(11):3035-3040. doi: 10.1039/d1na00140j. eCollection 2021 Jun 1.
Revolutionary microscopy technologies for aberration correction in spatial and energy aspects have exhibited continuous progress, pushing forward the information limit of materials research down to a scale of sub-angstrom and milli-electron voltage. Nevertheless, imaging quality could still suffer due to sample instability, the charging effect, which always comes along with electron microscopy characterizations. Herein, using a defocus estimation algorithm and an image feature tracking method, we quantitatively studied the image drifting dynamics induced by the charging on transmission electron microscopy (TEM) carrier grids with tunable electrical conductivity. Experimental evidence clarifies the debate about the charge types, proving that the irradiation of the electron beam induces a positive charge on the grid sample of poor electrical conductivity. Such charge accumulation accounts for subsequent imaging instability, including the increase of defocus and the drift of lateral images. Particularly, the competition between charging and discharging was found to dynamically modulate the propagation of electron beam, resulting in a periodically reciprocating movement on TEM images. These findings enrich understanding on the dynamic principle of charging effects as well as the details of image drifting behaviors. It also suggests specific attention on the importance of conductivity control on a TEM specimen, beyond all the efforts for instrumental improvements.
用于空间和能量方面像差校正的革命性显微镜技术不断取得进展，将材料研究的信息极限推进到亚埃和毫电子伏特尺度。然而，由于样品不稳定性以及电子显微镜表征中总是伴随的充电效应，成像质量仍可能受到影响。在此，我们使用散焦估计算法和图像特征跟踪方法，定量研究了具有可调电导率的透射电子显微镜（TEM）载网上充电引起的图像漂移动力学。实验证据澄清了关于电荷类型的争论，证明电子束照射会在导电性差的网格样品上诱导正电荷。这种电荷积累导致了后续的成像不稳定性，包括散焦增加和横向图像漂移。特别地，发现充电和放电之间的竞争动态地调节电子束的传播，导致TEM图像上的周期性往复运动。这些发现丰富了对充电效应动态原理以及图像漂移行为细节的理解。这也表明，除了对仪器进行改进的所有努力之外，还应特别关注TEM样品电导率控制的重要性。
