Modulation Effect of Substrate Interactions on Nucleation and Growth of MoS2 on Silica

Chemical vapor deposition is a well-established bottom-up technique to produce a high-quality single-crystal MoS2 film. In this technique, the substrate (e.g., silica) plays a crucial role in the segregation and chemical interaction of precursors to form grain-sized MoS2. However, the mechanisms of the surface interactions that influence the properties of MoS2 during growth are still poorly understood. Here, we combine ReaxFF reactive molecular dynamics simulations, density functional theory (DFT) calculations, and experimental growth of MoS2 to provide an atomic insight into the coupling between the surface chemistry and the MoS2 nucleation and growth on a silica surface. Our experimental results show that the dehydroxylated surface stays mainly inert during the MoO3 flow, while the presence of hydroxyl groups leads to MoO3 nucleation on the substrate. ReaxFF and DFT simulations further confirm that the reaction between MoO3 and the hydroxylated surface is both thermodynamically and kinetically driven, indicating that hydroxyl groups formed on silica enhance the chemical reactivity of the surface toward MoO3 molecules and promote the growth. Additionally, the MoS2 growth on the hydroxylated silica support initiates with MoO3 nucleation followed by the chalcogen-surface interactions. Moreover, the existence of the substrate catalyzes the growth by lowering the growth temperature, providing an effective way for energy saving and cost reduction. These results demonstrate the intricate role of surface engineering in controlling and promoting large-area MoS2 growth.