Atomistic reaction mechanism of CVD grown MoS 2 through MoO 3 and H 2 S precursors.

Chemical vapor deposition (CVD) through sulfidation of MoO 3 is one of the most important synthesis techniques to obtain large-scale and high-quality two-dimensional (2D) MoS 2 . Recently, H 2 S precursor is being used in the CVD technique to synthesize 2D MoS 2 . Although several studies have been carried out to examine the mechanism of MoS 2 growth in the presence of sulfur and MoO 3 precursors, the growth of MoS 2 in the presence of H 2 S precursor has largely remained unknown. In this study, we present a Reactive molecular dynamics (RMD) simulation to investigate the reaction mechanism of MoS 2 from MoO 3 and H 2 S precursors. The intermediate molecules formation, the reason behind those formations, and the surface compositions of MoO x S y H z during the initial steps of CVD have all been quantified. Surprisingly, a sudden separation of sulfur atoms from the surface was observed in the H 2 S precursor system due to the substantial oxygen evolution after 1660 K. The sulfur detachments and oxygen evolution from the surface were found to have a linear relationship. In addition, the intermediate molecules and surface bonds of MoS 2 synthesized by MoO 3 and H 2 S precursors were compared to those of a system using S 2 and MoO 3 precursors. The most stable subsidiary formation from the H 2 S precursor was found to be H 2 O, whereas in case of S 2 precursor it was SO. These results provide a valuable insight in the formation of large-scale and high-quality 2D MoS 2 by the CVD technique.