Ab initio calculations and ellipsometry measurements of the optical properties of the layered semiconductor In_4Se_3

摘要

In this work, we present a thorough study of the optical properties of the layered orthorhombic compound In_4Se_3. The dielectric function-real and imaginary parts, the complex refraction index, the reflectivity, the absorption coefficient, and the conductivity of In_4Se_3 were calculated with the inclusion of the spin-orbit interaction, using an ab initio FP-LAPW method based on DFT. Also, generalized ellipsometry was employed for more precise measurement of the anisotropic dielectric functions for polarization along crystal a, b, and c axes of orthorhombic absorbing In_4Se_3 single crystals cut approximately parallel to (100) at photon energies from 0.76 to 3.1 eV. Our experimental results show a good agreement with our calculations. We discuss the location and nature of the main optical peaks appearing in the spectra. The obtained optical functions display a rather anisotropic behavior, mainly in the infrared-visible region. Our results seem to be predictive to a high extension, given the scarce experimental information about its optical properties.