Ryu Gyeong Hee, Chan Ren-Jie
School of Materials Science and Engineering, Gyeongsang National University, Jinju, 52828, Republic of Korea.
Department of Materials, University of Oxford, 16 Parks Road, Oxford, OX1 3PH, UK.
Appl Microsc. 2020 Nov 30;50(1):27. doi: 10.1186/s42649-020-00047-2.
Transition metal dichalcogenides (TMD), which is composed of a transition metal atom and chalcogen ion atoms, usually form vacancies based on the knock-on threshold of each atom. In particular, when electron beam is irradiated on a monolayer TMD such as MoS and WS, S vacancies are formed preferentially, and they are aligned linearly to constitute line defects. And then, a hole is formed at the point where the successively formed line defects collide, and metal clusters are also formed at the edge of the hole. This study reports a process in which the line defects formed in a monolayer WS sheet expends into holes. Here, the process in which the W cluster, which always occurs at the edge of the formed hole, goes through a uniform intermediate phase is explained based on the line defects and the formation behavior of the hole. Further investigation confirms the atomic structure of the intermediate phase using annular dark field scanning transition electron microscopy (ADF-STEM) and image simulation.
过渡金属二硫属化物（TMD）由过渡金属原子和硫属离子原子组成，通常基于每个原子的反冲阈值形成空位。特别是，当电子束照射到诸如MoS和WS的单层TMD上时，优先形成S空位，并且它们线性排列以构成线缺陷。然后，在相继形成的线缺陷碰撞的点处形成一个孔，并且在孔的边缘也形成金属簇。本研究报道了单层WS片中形成的线缺陷扩展成孔的过程。在此，基于线缺陷和孔的形成行为，解释了总是出现在所形成孔边缘的W簇经历均匀中间相的过程。进一步的研究使用环形暗场扫描透射电子显微镜（ADF-STEM）和图像模拟确认了中间相的原子结构。
