Surface plasmon dispersion of a cluster-assembled silver nanoparticle film

We report an investigation with high-resolution electron-energy-loss spectr oscopy of a thin Ag him grown by deposition and aggregation of Ag-3(-) clus ters on graphite. We find the plasmon mode of the nanostructured film (part icle size similar to 10 nm) at about 3.85 eV near the Brillouin-zone center , representing a blueshift of 0.15eV with respect to the surface of a bulk Ag crystal. With increasing momentum parallel to the surface, the plasmon s hows a very shallow positive dispersion and a distinct broadening. The resu lts suggest a decrease in the s-d coupling in our nanoparticle film compare d with the bulk. [S0163-1829(99)15215-9].