Optical constants of gold blacks: Fractal network models and experimental data

Abstract

We demonstrate that the optical properties of gas-evaporated gold blacks can be qualitatively explained using fractal admittance network models. A consistent set of optical constants of gold black is obtained by performing a Kramers-Kronig analysis on literature data in the wavelength range from the near ultraviolet to the far infrared. In order to describe the optical properties we put forward two three-dimensional fractal network models. In one of them we consider a percolating backbone structure; in the other we also include effects of dangling ends and finite clusters. The shape of the absorption coefficient and refractive index spectra predicted by the models are in qualitative agreement with the experimental data.