Atomistic insight into the oxidation of monolayer transition metal dichalcogenides: from structures to electronic properties

Abstract

Monolayer transition metal dichalcogenides (TMDs) stand out in two-dimensional (2D) materials due to their potential applications in future microelectronic and optoelectronic devices. In experiments, field effect transistors (FET) based on the MoS₂ monolayer are sensitive to environmental gases, especially O₂. Thus, the oxidation of monolayer TMDs is a critical concern. By first-principles calculations, we reveal that a perfect single-layer sheet of TMDs stays intact when exposed in O₂ due to the weak physical adsorption of O₂. However, O₂ can be chemically adsorbed onto the monolayer of TMDs (including MoS₂, MoSe₂, MoTe₂, WS₂, WSe₂, and WTe₂) with single vacancies of chalcogen, which are the most common defects in realistic TMD materials. The adsorption configurations and dissociation behavior of the O₂ molecule at vacancy sites, as well as the possible diffusion behavior of oxygen adatoms on the TMD monolayer surface were explored. Oxidation significantly influenced the electronic properties of a defective MoS₂ monolayer, while other defective TMD monolayers (especially MoTe₂ and WTe₂) suffered less from oxidation. Our theoretical results provide valuable atomistic insight into the oxidation of TMD monolayers and are useful for the future design of TMD-based 2D devices.