Hetero-epitaxial growth of hexagonal boron nitride (h-BN) from the edges of graphene domains or vice versa has been widely observed during synthesis of in-plane heterostructures of h-BN-G on Rh(111), Ir(111), and even Cu foil. We report that on a strongly coupled Re(0001) substrate via a similar two-step sequential growth strategy, h-BN preferably nucleated on the edges of Re(0001) steps rather than on the edges of existing graphene domains. Statistically, one-third of the domain boundaries of graphene and h-BN were patched seamlessly, and the others were characterized by obvious "defect lines" when the total coverage approached a full monolayer. This imperfect merging behavior can be explained by translational misalignment and lattice mismatch of the resulting separated component domains. According to density functional theory calculations, this coexisting patching and non-patching growth behavior was radically mediated by the strong adlayer-substrate (A-S) interactions, as well as the disparate formation energies of the attachment of B-N pairs or B-N lines along the edges of the Re(0001) steps versus the graphene domains. This work will be of fundamental significance for the controllable synthesis of in-plane heterostructures constructed from two-dimensional layered materials with consideration of A-S interactions.
Keywords: edges of Re steps and graphene domains; graphene and hexagonal boron nitride heterostructures; preferable nucleation; ultra-high-vacuum scanning tunneling microscopy/spectroscopy.