Computational Synthesis of MoS₂ Layer by the Direct Sulfidation of MoO₃ Surfaces: A Reactive Molecular Dynamics Study

Monolayer MoS₂ is a promising candidate for next-generation electric devices due to its outstanding electronic, optical, and chemical properties. Chemical vapor deposition (CVD) is the most effective method to bring this layered material into mass production for a wide range of nanoscale applications. During CVD synthesis, a direct sulfidation of MoO₃ surfaces is a critical reaction event, leading to mono/few MoS₂ layers on substrates. However, an atomic-level understanding of the sulfidation process remains elusive. In this work, we present first-principles informed and validated reactive molecular dynamics simulations of the direct sulfidation of MoO₃ surface. We find that reduction and sulfidation events locally occur on the MoO₃ surface, resulting in surface defects whereas the healing of the defects could be controlled by further introduction of sulfur precursors. Our work clarifies an origin of surface defects on MoS₂ layers as well as optimized conditions for the defect healing process, allowing us to refine scalable CVD techniques for synthesis of defect-free MoS₂ layers.