Surface Roughness and the Absorption of Electromagnetic Waves in Simple Metals

Abstract

The reflection of electromagnetic waves impinging normally on the rough surface of a simple metal is theoretically investigated for frequencies small enough so that band effects are minimal. This is done by first examining the effects of the metallic surfaces on the single-particle states. The "effective roughness" for the single-particle states depends on their frequency, wave vector, and mean free path. It is found that the derivation of the reflectivity from the specular limit depends on an rms surface roughness depth when the characteristic roughness wavelength is smaller than the electron mean free path. If the surface is sufficiently rough on a longer-wavelength scale, it is found that the reflectivity can be smaller than that predicted by assuming that all electrons are diffusely reflected at the surface.