Electronic structure of carbidic and graphitic carbon on Ni(111)

The electronic structure of carbon overlayers on Ni(111) has been investigated by using photoemission, energy-loss, and ionization-loss spectroscopy techniques. The combined use of these spectroscopies gives a detailed picture of these surfaces which have important catalytic implications. The carbidic carbon overlayer shows states at ∼1-, 4.2-, and 13-eV binding energy. Of particular significance is the detection (both in photoemission and in ionization-loss spectroscopy) of a carbon-derived state very near the Fermi level, in excellent agreement with recent theoretical predictions. The graphitic overlayer has an electronic structure very close to the electronic structure of pure graphite. We detect, however, an almost rigid shift of both valence and conduction bands which points to a charge transfer of about 0.02 electrons per carbon atom between the nickel substrate and the graphitic overlayer.