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 int ercalation of gold atoms underneath a monolayer of graphite formed on Ni(11 1), have been investigated by angle-resolved photoemission spectroscopy (PE S) and high-resolution electron-energy-loss spectroscopy (HREELS). Modifica tions of both electronic structure and vibrational properties due to the pr esence of the intercalated Au monolayer between the graphite monolayer and Ni(111) are reported. The surface intercalation of the gold atoms underneat h the graphite monolayer leads to a "stiffennng" of the graphite-derived ph onon modes and to an energetic shift of the graphite-derived pi, sigma elec tronic states in the valence band toward lower binding energies. The observ ed changes of the PE and HREEL spectra are explained by the saturation of t he active Ni(d) bonds by the intercalated gold atoms and by the weakening o f the interaction between graphite monolayer and substrate, due to the bloc kage of the graphite Ct (pi)-Ni(d) hybrid bonds.