(407a) Atomically-Precise Moiré Fringes in 2D Van Der Waals Heterostructures of Graphene and Hexagonal Boron Nitride

The van der Waals force-bound heterostructures of isostructural and isoelectronic graphene and hexagonal boron nitride (h-BN) offer a platform for fundamental phenomena evolving from the resultant Moiré superlattices. Such phenomena in two-dimensional (2D) planar sp² lattice stacks of graphene/h-BN or graphene/h-BN/graphene or h-BN/graphene/h-BN are sensitive to their atomic-scale assembly. Current techniques rely on physical or chemical transfer of both h-BN and graphene to build the 2D sandwich heterostructure circuits. These transfer-steps not only introduce the interfacial polymeric and metallic heteroatom impurities but also creates random or mis-aligned regions in the 2D-heterostructures. Here, we report one-dimensional (1D) Moiré fringes in the graphene and h-BN heterostructures developed through direct stacking of graphene and h-BN via a bottom-up all-chemical vapor deposition (CVD) strategy. Polycrystalline layer of h-BN is first synthesized via a surface chemical-interaction guided process on silicon-based gate-dielectric substrate. Then the graphene layer is grown via grain-boundary diffusion of catalytically produced carbon radicals through a polycrystalline metal film on h-BN. Finally, removing the thin metal film (and any graphene on it) results in graphene/h-BN heterostructures with a sharp, defect-free, and atomically-precise interfaces; as confirmed by scanning resonant Raman spectroscopy and X-ray photoelectron spectroscopy studies. The directly-grown, van der Waals bound graphene/h-BN heterostructures exhibit 1D Moiré fringes with a periodic pitch of ≈10 Ã… at a rotation angle of 16^o. Further, the low-temperature transport measurements reveal the charge carrier mobility of 100 cm²v^-1s^-1, 2-orders of magnitude higher than the graphene/h-BN heterostructure produced via co-segregation process. Futuristically, this all-CVD direct-growth strategy will be a transformative approach for scalable production of van der Waals heterostructures to realize complex 2D circuitry and fundamental physics phenomena.