Plasmon resonance shift during grazing incidence ion sputtering on Ag(001)

Grazing incidence ion sputtering was used to create shallow ripple patterns on a Ag(001) surface. The anisotropic plasmon resonance associated with this ripple pattern can be sensitively measured with Reflection Anisotropy Spectroscopy. A slight red shift of the resonance energy is observed with increasing ion fluence. The observed resonance feature is described well with a skewed Lorentzian line shape. This line shape is the small roughness length scale limit of the Rayleigh Rice perturbation approach. The width of this line shape is directly related to imaginary part of the dielectric function, which shows a roughness induced reduction of the electron mean free path. The observed change in resonance energy and strength with ion fluence is discussed.