Electroreflectance spectra of Ag(111) electrodes

Electroreflectance (ER) spectra of Ag(111) evaporated electrodes on mica in aqueous electrolytes were measured within the wavelength range of 500 to 200 nm for p- and s-polarized light as a function of the angle of incidence, bias potential and surface roughness. These spectra show structures which were not seen in previously obtained ER spectra on slightly rough, polycrystalline Ag electrodes. The effect of volume and surface plasma excitation on the spectra is clearly indicated. The experimental results cannot be reproduced satisfactorily by any currently employed theoretical model which takes only free electron effects into account. The influence of the electric field on the bound electrons in the surface layer obviously cannot be neglected. It is demonstrated that the surface plasma resonance is shifted in energy by the applied electric field.