Moire Superstructures of Graphene on Faceted Nickel Islands

Using scanning tunneling microscopy and spectroscopy in combination with density functional theory calculations; we investigated the morphology and electronic structure of monolayer graphene grown on the (111) and (110) facets of three dimensional nickel islands on highly oriented pyrolytic graphite substrate. We observed graphene domains exhibiting hexagonal and striped moire patterns with periodicities of 22 and 12 angstrom, respectively, on (111) and (110) facets of the Ni islands Graphene domains are also observed to grow, as single crystals, across adjacent facets and over facet boundaries Scanning tunneling spectroscopy data indicate that the graphene layers are metallic on both Ni(111) and Ni(110), in agreement with the calculations. We attribute this behavior to a strong hybridization between the d bands on Ni and the pi bands of carbon. Our findings point to the possibility of preparing large area epitaxial graphene layers even on polycrystalline Ni substrates.