Nanoscale thickness-dependent dielectric function for Au thin films

Abstract

Metallic materials at the nanoscale (nanoparticles, nanowires and thin films) have relevant roles in different applications. Applications are based on the nanoscale's optical properties, which are based on knowledge of the size-dependent dielectric function properties. In this proposal, an analytical expression for the dielectric function as a function of frequency and thickness of Au nanometric films is derived, considering the contributions of free and bound electrons. For free electron contribution, Drude model was used to determine the model parameters dependent on film thickness. As for the bound electron, its contribution for short wavelengths is the same for all thicknesses analyzed and can be set equal to the bulk contribution. Finally the dielectric function is rewritten analytically, in terms of the bulk dielectric function plus two corrective terms dependent on the film thickness.