Substrate-Dependent Growth Mode Control of MoS₂ Monolayers: Implications for Hydrogen Evolution and Field-Effect Transistors

The control of domain sizes provides a powerful means to engineer the characteristics of monolayer (ML) MoS2 films for specific applications including catalysts for hydrogen evolution and thin-film transistors. Here, we report an efficient way to control domain structures of MoS2 by substrate-dependent growth mode control. Deterministic control of growth modes, associated with catalytic intermediates, is introduced by utilizing different growth substrates in metal-organic chemical vapor deposition (MOCVD) of ML MoS2. Na-Mo-O eutectic alloys formed by a soda lime (SL) substrate dominate the growth based on a vapor-liquid-solid (VLS) process, resulting in large-crystalline domains of MoS2 with a reduced density of liquid nuclei. On the other hand, MoO3-x seeds formed from an alkali aluminosilicate (AA) substrate accelerate nucleation via a vapor-solid-solid (VSS) process for nanocrystalline domains. ML MoS2 of nanocrystalline domains resulted in efficient hydrogen evolution reactions (HERs), while large-domain films showed better electron conductivity.