Conversion of multilayer graphene into continuous ultrathin sp 3-bonded carbon films on metal surfaces

摘要

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 sp 3 orbitals and metal surface d z 2 orbitals. The induced electronic gap states and spin moments in the carbon layers are confined in a region within 0.5â.nm of the metal surface. Whether the conversion occurs depend on the fraction of hydrogenated (fluorinated) C atoms at the outer surface and on the number of stacked graphene layers. In the analysis of the Eliashberg spectral functions for the sp 3 carbon films on a metal surface that is diamagnetic, 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 computational results suggest a route to experimental realization of large-area ultrathin sp 3-bonded carbon films on metal surfaces.