(566a) Atomically-Precise Van Der Waals Heterostructures of Graphene and h-BN for 2D Circuits

Van der Waals heterostructures of isostructural and isoelectronic graphene and hexagonal boron nitride (h-BN) offer a singular platform to study fundamental physics phenomena such as the origin of energy bandgap opening at the Dirac point in graphene, Hofstadter’s butterfly effect in graphene, chiral quantum states of Dirac electrons, and the detection of topological currents. Such phenomena in graphene/h-BN or graphene/h-BN/graphene or h-BN/graphene/h-BN planar sp² lattice stacks are extremely sensitive to their process of synthesis and nanoscale assembly. Current techniques mostly rely on the mechanical or chemical transfer of both h-BN and graphene to build the 2D sandwich heterostructures, which introduces the interfacial polymeric and metallic heteroatom contaminations. Here we report the direct, transfer-free, and atomically-precise development of both vertical and lateral heterostructures of graphene and h-BN via a bottom-up all-chemical vapor deposition (CVD) strategy. This 3-step approach combines: (i) the catalyst-free nucleation of h-BN on oxide and nitride-based gate-dielectric substrates via surface chemical-interaction guided mechanism; (ii) physical deposition of a thin, polycrystalline, and low-carbon solubility metal film on h-BN; and (iii) synthesis of graphene on h-BN via diffusion of catalytically produced carbon radicals through polycrystalline metal grain-boundaries and their crystallization at the interface of metal film and h-BN. The directly-grown, van der Waals bound graphene/h-BN heterostructures with atomically-precise, sharp, and contamination-free interfaces are obtained by carefully removing the top graphene and thin metal layers. The structural integrity, atomic registry, crystal quality and orientations of graphene/h-BN stacks are typified by scanning resonant Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and atomic force microscopy. Further, the low-temperature quantum transport measurements reveal the charge carrier mobility of 100 cm²v^-1s^-1. 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.