Band structure and optical constants of SnS2 single crystals

Absorption (K), reflection (R) and wavelength modulated transmission (Delta T/Delta lambda) spectra in SnS2 crystals of hexagonal phase (space group P6(3)/mmc) were investigated in temperature interval from 300 to 10 K. It was established that indirect band gap (E-g(ind) - 2.403 eV) is due to unpolarized indirect transitions between Gamma and M points of Brillouin zone. A minimal direct band gap (E-g(dir) - 2.623 eV) in E parallel to b polarization is formed by direct allowed transitions and in E perpendicular to b polarization (2.698 eV) by forbidden transitions in Gamma point of Brillouin zone. A magnitude of refractive index (n) changes from 3 to 4 and has a maximum at 2.6 eV. Optical functions (n, k, epsilon(1) and epsilon(2)) in energy region E > E-g (3-6.5 eV) were calculated from measured reflection spectra by Kramers-Kronig analysis. Features observed in reflection and optical function spectra were assigned to electron transitions. This electron transitions were localized in framework of theoretically calculated band structure.