An ellipsometric study of thin-film structures of amorphic hydrogenized carbon and gold nanoparticles

Optical сonstants of an amorphous hydrogenated carbon (a-C:H) film and its hybrid structure with granular gold film before and after annealing at 300$^\circ$C have been investigated by spectral ellipsometry. Dispersions $n(\lambda)$ and $k(\lambda)$ of the a-C:H film and its thickness have been identified using the Cauchy approximation. The spectral features of the layer of Au plasmon nanoparticles deposited on the a-C:H surface have been modeled in the form of an effective medium and Lorentz oscillator. The parameters of the films and their thickness have been determined by fitting the calculated spectra to the $\psi(\lambda)$ and $\Delta(\lambda)$ ellipsometric spectra. The obtained data have been used to determine the Lorentz oscillator parameters in the model of an a-C:H/Au two-layer structure. The intensity of the maxima in the $n$ and $k$ spectra increased, their position shifted to the blue region, and the half-width of the bands decreased as a result of the a-C:H/Au structure annealing. The observed changes in ellipsometric spectra are fully consistent with the spectrophotometric data of this structure.