Effect of liquids on the Drude dielectric function of Ag and Au films

Spectroscopic ellipsometric measurements were made of the free-electron dielectric functions of Ag and Au films in air and immersed in dielectric liquids of different refractive indexes. The effects seen by Gugger et al. were reproduced for Ag and Au films prepared similarly to theirs, and in Ag films with larger grains. Different effects were seen with an (oxidized) single crystal of Ag and a single crystal of Au. The ''anomalous'' data could be fitted with an effective-medium model by assuming that the liquid penetrates all, or most, of the intergrain regions within the optical penetration depth. The dielectric functions of ''ideal'' Ag and Au samples were obtained from fits with an effective-medium model.