Single-layer $1T'$-MoS$_2$ under electron irradiation from $ab$ $initio$ molecular dynamics

TL;DR

This study uses ab initio molecular dynamics to understand how electron irradiation affects 1T'-MoS2, revealing thresholds for damage, defect formation, and vacancy behavior to guide microscopy and defect engineering.

Contribution

It provides detailed atomic-scale insights into electron beam interactions with 1T'-MoS2, including damage thresholds and defect dynamics, aiding precise manipulation.

Findings

Electron beams below 75 keV do not cause knock-on damage.

Displacement energies vary between sulfur atoms and layers.

Careful beam tuning can induce ordered defects.

Abstract

Irradiation with high-energy particles has recently emerged as an effective tool for tailoring the properties of two-dimensional transition metal dichalcogenides. In order to carry out an atomically-precise manipulation of the lattice, a detailed understanding of the beam-induced events occurring at the atomic scale is necessary. Here, we investigate the response of $1T'$-MoS$_2$ to the electron irradiation by $ab$ $initio$ molecular dynamics means. Our simulations suggest that an electron beam with energy smaller than 75 keV does not result in any knock-on damage. The displacement threshold energies are different for the two nonequivalent sulfur atoms in $1T'$-MoS$_2$ and strongly depend on whether the top or bottom chalcogen layer is considered. As a result, a careful tuning of the beam energy can promote the formation of ordered defects in the sample. We further discuss the effect of the electron irradiation in the neighborhood of a defective site, the mobility of the sulfur vacancies created and their tendency to aggregate. Overall, our work provides useful guidelines for the imaging and the defect engineering of $1T'$-MoS$_2$ using electron microscopy.