Plasmon Confinement in Ultrathin Continuous Ag Films

Abstract

We investigate the effect of film thickness and granularity on the collective excitation of nanostructured ultrathin Ag films deposited on $\mathrm{Si}(111)7\ifmmode\times\else\texttimes\fi{}7$ by energy loss spectroscopy and low energy electron diffraction to obtain structural and spectroscopic information. For continuous thin films we find that the plasmon frequency at a vanishing wave vector scales with the surface-to-volume ratio of the grains, i.e., as the Mie resonance of separated clusters, instead of with inverse thickness. This indicates a confinement of the plasmon into single domains, in spite of metallic conductivity.