Effects of annealing on the attenuated-total-reflection spectra of cold-evaporated silver films

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Abstract
We have used attenuated-total-reflection (ATR) techniques to study the ``annealing'' of thin Ag films evaporated onto a liquid-nitrogen-cooled substrate under ultrahigh-vacuum conditions. We used the Kretschmann configuration for our ATR measurements and scanned the angle of incidence at fixed wavelengths. The ATR dips of these ``cold-evaporated'' films are much broader and shallower than those of Ag films evaporated at room temperature and occur at greater angles of incidence, but warming these cold-evaporated Ag films to room temperature irreversibly changes their ATR dips to ones resembling those of room-temperature-deposited films. This change occurs most rapidly in the same temperature range at which the surface-enhanced Raman scattering activity of these films irreversibly diminishes. We fitted the ATR data to a simple phenomenological model which describes the Ag film by a complex effective dielectric constant.