Sputtering-induced modification of the electronic properties of Ag/Cu(111)

High-resolution electron energy loss spectroscopy has been used to study the electronic properties of Ag thin films deposited on Cu(1 1 1) and modified by Ar+ sputtering. Ion sputtering strongly modifies the loss function in the region of single-particle transition as deduced from the appearance of sputtering-induced spectral features in the valence band. In contrast to unmodified Ag systems, in the sputtered films the centroid of the induced charge of the surface plasmon lies in the close vicinity of the jellium edge. In these modified Ag films, Landau damping processes are activated beyond a critical energy of 3.83 eV and a threshold wave vector of 0.2 angstrom(-1). Moreover, we find that plural plasmonic losses arise upon increasing the Ar+ dose. A comparison with the case of the sputtered Ag(1 0 0) surface is presented throughout the paper.