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.