Thin film optical properties in relation to film structure

Abstract

The optical properties of solids may be strongly influenced by their crystalline, morphological and compositional structure. In this paper we review the effect of quench condensation on the optical properties of metal films. A few pure metals may be made amorphous by quench condensation; however, most metal films are microcrystalline. We review the spectra of the amorphous metals and give an account of the additional absorption found in many microcrystalline films. This effect is similar to effects found in metal films with rough surfaces, in discontinuous thin films and in two-phase metal-insulator films and is caused by the excitation of surface plasmons propagating along grain boundaries. Theoretical calculations which support this explanation will be presented. A brief account of the effect of thermal disorder on the optical response is included in the discussion, and we also give examples of the effect of allotropic phase transformations on the optical properties of selected solids.