Influence of Grain Boundaries and Lattice Defects on the Optical Properties of Some Metals

Abstract

A simple theory is developed to study the influence of grain boundaries and lattice defects on the optical properties of metals. It is shown that even for well-annealed thin-film samples the influence of grain boundaries on the optical properties is not negligible when the reflectivity is high. The model is used to show that the anomalous absorptivity in alkali-metal films evaporated onto cold substrates recently reported by Palmer and Schnatterly is due predominantly to a plasma resonance in the grain boundaries. It is also found that the non-Drude behavior of Ag in the visible and the supplementary absorption in poorly crystallized Au films, observed by Devant and Theye, most probably is due to such plasma resonances in the grain boundaries.