Atomistic reaction mechanism of CVD grown MoS through MoO and HS precursors.

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