Atomistic Mechanism of MoS₂ Oxidation Induced by Reactive Superoxide and Ozone Treatment: A First-principles Study

While two-dimensional transition metal dichalcogenides (TMDCs) are emerging as promising candidates for next-generation microelectronic and other technologies, the oxidation and degradation effects on TMDCs with the atomic-scale thicknesses remain a significant bottleneck for their practical applications. Despite its significance, an atomic-scale understanding of oxidation mechanism on TMDCs is yet largely underexplored. Herein, carrying out standard density functional theory and room-temperature ab-initio molecular dynamics calculations, we systematically explore the oxidation mechanism in monolayer as well a few-layer MoS₂ under different gaseous environment such as containing regular oxygen (O₂), superoxide (O₂^-), and ozone molecule (O₃). We propose plausible pathways for SO₂ formation wherein O₂^- and O₃ readily form SO₂, however, O₂ has a high adsorption barrier of 1.96 eV on MoS₂ surface. We also find that the bending and opening the edges is the key step that allows the self-limiting layer-by-layer oxidation of MoS₂ and identify an easier penetration of O₂^- into the open interlayer region bearing small energy barrier compared to O₂. Our findings may provide the mechanistic importance of controlling TMDCs heterostructures and the strategies to prevent the oxidation of TMDCs.