Optical properties of amorphous metallic gold-silicon alloys

Abstract

The optical properties of amorphous films of ${\mathrm{Au}}_{1\ensuremath{-}x}{\mathrm{Si}}_{x}$ alloys were studied in the spectral region from 0.01-6.2 eV as a function of composition in the range $0.13\ensuremath{\le}x\ensuremath{\le}0.50$. The reflectivity, dielectric function, and energy-loss spectra are presented. As discussed in a previous paper, the extremely short electron relaxation times give rise to some unusual features in $\ensuremath{\epsilon}(\ensuremath{\omega})$. The onset of interband transitions shifts to higher energy as the silicon concentration is increased. The measured shifts are in surprisingly good agreement with those predicted by a simple rigid-band approximation.