Kretschmer Silvan, Lehnert Tibor, Kaiser Ute, Krasheninnikov Arkady V
Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany.
Central Facility for Electron Microscopy, Group of Electron Microscopy of Materials Science, Ulm University, Ulm 89081, Germany.
Nano Lett. 2020 Apr 8;20(4):2865-2870. doi: 10.1021/acs.nanolett.0c00670. Epub 2020 Mar 26.
Production of defects under electron irradiation in a transmission electron microscope (TEM) due to inelastic effects has been reported for various materials, but the microscopic mechanism of damage development in periodic solids through this channel is not fully understood. We employ non-adiabatic Ehrenfest, along with constrained density functional theory molecular dynamics, and simulate defect production in two-dimensional MoS under electron beam. We show that when excitations are present in the electronic system, formation of vacancies through ballistic energy transfer is possible at electron energies which are much lower than the knock-on threshold for the ground state. We further carry out TEM experiments on single layers of MoS at electron voltages in the range of 20-80 kV and demonstrate that indeed there is an additional channel for defect production. The mechanism involving a combination of the knock-on damage and electronic excitations we propose is relevant to other bulk and nanostructured semiconducting materials.
对于各种材料，已有报道称在透射电子显微镜（TEM）中由于非弹性效应在电子辐照下会产生缺陷，但通过该通道在周期性固体中损伤发展的微观机制尚未完全理解。我们采用非绝热的埃伦费斯特方法，结合约束密度泛函理论分子动力学，模拟了二维MoS₂在电子束下的缺陷产生。我们表明，当电子系统中存在激发时，在远低于基态撞击阈值的电子能量下，通过弹道能量转移形成空位是可能的。我们进一步在20 - 80 kV电子电压范围内对单层MoS₂进行了TEM实验，并证明确实存在额外的缺陷产生通道。我们提出的涉及撞击损伤和电子激发相结合的机制与其他块状和纳米结构半导体材料相关。
