Unlocking of Schottky Barrier Near the Junction of MoS₂ Heterostructure Under Electrochemical Potential

The exploration of heterostructures composed of two-dimensional (2D) transition metal dichalcogenide (TMDc) materials has garnered significant research attention due to the distinctive properties of each individual component and their phase-dependent unique properties. Using the plasma-enhanced chemical vapor deposition (PECVD) method, we analyze the fabrication of heterostructures consisting of two phases of molybdenum disulfide (MoS₂) in four different cases. The initial hydrogen evolution reaction (HER) polarization curve indicates that the activity of the heterostructure MoS₂ is consistent with that of the underlying MoS₂, rather than the surface activity of the upper MoS₂. This behavior can be attributed to the presence of Schottky barriers, which include contact resistance, which significantly hampers the efficient charge transfer at junctions between the two different phases of MoS₂ layers and is mediated by van der Waals bonds. Remarkably, the energy barrier at the junction dissipates upon reaching a certain electrochemical potential, indicating surface activation from the top phase of MoS₂ in the heterostructure. Notably, the 1T/2H MoS₂ heterostructure demonstrates enhanced electrochemical stability compared to its metastable 1T-MoS₂. This fundamental understanding paves the way for the creation of phase-controllable heterostructures through an experimentally viable PECVD, offering significant promise for a wide range of applications.