Optical properties of epitaxialCoSi2on Si from 0.062 to 22.3 eV

The optical constants of epitaxial ${\mathrm{CoSi}}_2$ films on Si from 0.062 to 22.3 eV have been determined by ellipsometry and reflectance measurements. The energy dependencies of the dielectric functions show Drude behavior at energies lower than ∼0.2 eV with Drude parameters ħ${\mathrm{\omega }}_{\mathit{p}}$=(5.8±0.2) eV and ħ/τ=(0.09±0.02) eV. The energy-loss function, calculated from the optical constants, shows two peaks that correspond to the screened plasma oscillation and volume plasma oscillation of all valence electrons. Using the measured optical constants, a composite thin film of epitaxial ${\mathrm{CoSi}}_2$ particles embedded in Si is shown to have the absorptance peak due to a surface-plasmon resonance in the ${\mathrm{CoSi}}_2$ particles. The peak shifts to higher energy as the ellipsoidal particles become more elongated, in good agreement with recent observations by Fathauer et al. [Phys. Rev. B 44, 1345 (1991)].