Optical properties of silver films deposited at low temperatures

Abstract

The reflectance spectrum of quench-condensed silver films was studied as a function of film temperature and thermal history, using an uv-visible stress-modulator ellipsometer. Films deposited at low temperatures were found to exhibit an anomalous absorption in the visible region of the spectrum. This absorption was attenuated and receded to lower wavelengths as the film was annealed. The spectra were successfully reproduced by assuming that films deposited at low temperatures were rough and that the roughness could be modeled by means of a two-dimensional metallic colloid whose optical conduction resonance accounted for the anomalous absorption. The relationship between the surface morphology of these low-temperature condensed films and their ability to give rise to surface-enhanced Raman scattering is discussed.