The nature of the inelastic background in surface enhanced raman scattering spectra of coldly-deposited silver films. The role of active sites

Abstract The shape of the background spectrum in the surface enhanced Raman scattering (SERS) has been studied on coldly deposited silver films over a broad interval of the Stokes-shift frequencies. The background intensity increases with the frequency, reaches its maximum at the frequencies ≅3700 cm −1 and then decreases slowly. Such a behaviour is well described by the theory based on a model which assumes the presence in the vicinity of the Fermi level of narrow quasi-stationary one-electron states localized near surface defect sites of a coldly deposited silver film. The inelastic light scattering caused by fluctuations in the number of electrons occupying these states leads to a strong background signal.