Quantum Molecular Dynamics Study on Sufidation Process of Molybdenum Oxide

Molybdenum disulfide (MoS$_{\mathrm{2}})$ monolayer, a direct bandgap semiconductor, is a promising candidate for future electronics applications due to its unique mechanical and electronic properties, for which fundamental understanding of growth processes is indispensable. \textit{In situ} transmission electron microscopy (TEM) study has shown that MoS$_{\mathrm{2}}$ nanocrystals are formed from a submonolayer molybdenum oxide dispersed on an oxide support by sulfidation in an H$_{\mathrm{2}}$S/H$_{\mathrm{2}}$ atmosphere. Time-resolved TEM images revealed that single-layer MoS$_{\mathrm{2}}$ nanocrystals form preferentially and that multi-layer nanocrystals form later in the sulfidation process. Here, we use quantum molecular dynamics simulation to investigate the sulfidation process of molybdenum oxide monolayer in H$_{\mathrm{2}}$S/H$_{\mathrm{2}}$ atmosphere. Simulation results identify key reaction pathways and intermediate products for MoS$_{\mathrm{2}}$ formation. We also quantify the interplay between H$_{\mathrm{2}}$ and those intermediate products. These atomistic mechanisms not only explain experimental results but also shed light on controlled growth of MoS$_{\mathrm{2}}$ monolayers.