EFFECTS OF MORPHOLOGY ON CHARGE TRANSFER PROPERTIES OF ULTRATHIN METALLIC FILMS ON GRAPHITE NANOSTRUCTURES

Abstract

The work function on graphitic nanostructures coated with gold, platinum and chromium is reported to be significantly modified by the size and density of the metal nanoparticles. Surface potentials on gold and platinum nanoparticles increased to 1.4 V, much higher than that of the bulk metals recorded at 0.45 V and 0.6 V, respectively. On chromium, a sign inversion in the surface potential (SP) was observed with -2 V measured on small nanoparticles and -0.9 V for bulk chromium. The change in sign is shown to result from an inversion in graphite Fermi level, consistent with known doping properties. A relation of the surface potentials with the resulting dipole confirms an occurrence of charge transfer from the metal nanoparticles to the graphitic nanostructure. The charge transfer increased from 0.04 eV to 0.27 eV for nanoparticles ranging between 0.1 nm and 1 nm. These findings demonstrate that besides the choice of metal, morphology of the film can be used to control electronic structure at metal-graphene/graphite interface.