Optical Functions of Chromium Disilicide Epitaxial Films in the Energy Range of 0.087-6.2 eV: Calculation Based on the Optical-Spectroscopy Data

摘要

Optical functions of the A-type CrSi_2 epitaxial films were calculated from the reflection-spectra data in the energy range of 0.28-6.2 eV with the use of the Kramers-Kronig relations and the difference-method extrapolation and also from the reflection and transmission spectra of the CrSi_2-film-Si(111)-substrate system in the transparency region (0.087-1.1 eV). A comparative analysis demonstrated that the values of the extinction coefficient k and the imaginary part ε_2 of the dielectric constant are excessively large in calculations based on the Kramers-Kronig relations in the energy range of 0.5-0.85 eV; negative values of k and ε_2 were obtained for energies below 0.35 eV. The principal special features of the energy-band structure of the A-type CrSi_2 epitaxial films are a low density of combined states in the regions of the first (0.37 eV) and the second (0.73 eV) direct band-to-band transitions, a sharp increase in the combined density of states in the region of the third direct band-to-band transition at 0.93 eV, and the emergence of a more pronounced structure in the transitions within the energy range of 2.5-6.2 eV.