Advanced Physical Research

The optical properties of the layered binary semiconductor compound In₂Se₃ were studied using spectral ellipsometry in the photon energy range of 0–7 eV. Based on the measured ellipsometric parameters, the complex dielectric function ε[ω] = ε₁[ω] + iε₂[ω] was calculated, and the refractive index [n], absorption coefficient [k], absorption coefficient [α], and reflectance [R] were determined. It was found that ε₁ reaches a maximum of 9.43 at 2.63 eV, while ε₂ has a maximum of 9.95 at 4.65 eV. The refractive index increases to 3.14 at 2.66 eV and then decreases to 1.48 at 6.24 eV. These results indicate strong light limitation in the visible range and high transparency in the ultraviolet region. The absorption coefficient exhibits a sharp maximum near 5.31 eV, and the absorption spectrum is characterized by a linear increase up to 5.0 eV with subsequent broadened maxima. The reflectance spectra confirm the presence of pronounced light-matter interaction. Spectral analysis of the energy loss function and effective density of states revealed maxima in the range of 5.3–5.6 eV, confirming the ability of In₂Se₃ to support plasmonic excitations. The optical conductivity spectrum exhibits clearly defined maxima and minima, indicating electronic transitions and frequency-dependent charge transfer.