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Conversion of multilayer graphene into continuous ultrathin sp3-bonded carbon films on metal surfaces

The conversion of multilayer graphenes into sp^3-bonded carbon films on metal surfaces (through hydrogenation or fluorination of the outer surface of the top graphene layer) is indicated through first-principles computations. The main driving force for this conversion is the hybridization between carbon sp^3 orbitals and metal surface dz^2 orbitals. The induced electronic gap states in the carbon layers are confined in a region within 0.5 nm of the metal surface. Whether the conversion occurs depend on the fraction of hydrogenated (fluorinated) C atoms and on the number of stacked graphene layers. In the analysis of the Eliashberg spectral functions for the sp^3 carbon films on diamagnetic metals, the strong covalent metal-sp^3 carbon bonds induce soft phonon modes that predominantly contribute to large electron-phonon couplings, suggesting the possibility of phonon-mediated superconductivity. Our results suggest a route to experimental realization of large-area ultrathin sp^3-bonded carbon films on metal surfaces.