Large-Scale Self-Limiting Synthesis of Monolayer MoS₂ via Proximity Evaporation from Mo Films

The large-scale synthesis of two-dimensional transition metal dichalcogenides has been actively investigated in recent years. Here, we introduce a nonconventional synthesis process of 2-in.-scale monolayer MoS₂ with fairly good uniform coverage, which is based on a unique reaction mechanism due to the self-limiting precursor source in a proximity reaction environment with a distance of only ∼0.5 mm from the reaction zone. The large-scale MoS₂ monolayer film was successfully synthesized using an atmospheric pressure chemical vapor deposition reaction of precursor Mo film in flowing H₂S gas through an indirect sulfurization sequence with the oxidized Mo species. The short distance of ∼0.5 mm provides a unique advantage of uniformity with the self-limiting reaction due to the limited MoO_3‑x supply. The chemical states of the precursor and deposited films at reaction temperatures were investigated to determine the reaction mechanism of the synthesis. This processing technique is extendable to other two-dimensional materials demanding large-scale coverage with good uniformity.