Surface intercalation of gold underneath a graphite monolayer on Ni(111) studied by angle-resolved photoemission and high-resolution electron-energy-loss spectroscopy

Quasi-two-dimensional intercalationlike systems, synthesized by surface intercalation of gold atoms underneath a monolayer of graphite formed on Ni(111), have been investigated by angle-resolved photoemission spectroscopy (PES) and high-resolution electron-energy-loss spectroscopy (HREELS). Modifications of both electronic structure and vibrational properties due to the presence of the intercalated Au monolayer between the graphite monolayer and Ni(111) are reported. The surface intercalation of the gold atoms underneath the graphite monolayer leads to a "stiffennng" of the graphite-derived phonon modes and to an energetic shift of the graphite-derived pi, sigma electronic states in the valence band toward lower binding energies. The observed changes of the PE and HREEL spectra are explained by the saturation of the active Ni(d) bonds by the intercalated gold atoms and by the weakening of the interaction between graphite monolayer and substrate, due to the blockage of the graphite Ct (pi)-Ni(d) hybrid bonds.