Band structure and optical constants of SnS2 single crystals

Abstract

Absorption ( K ), reflection ( R ) and wavelength modulated transmission (Δ T /Δ λ ) spectra in SnS2 crystals of hexagonal phase (space group P 6 3 / mmc ) were investigated in temperature interval from 300 to 10 K. It was established that indirect band gap (${{{\boldsymbol{E}}}_{{\boldsymbol{g}}}}^{{\boldsymbol{ind}}}$ - 2.403 eV) is due to unpolarized indirect transitions between Γ and M points of Brillouin zone. A minimal direct band gap (${{{\boldsymbol{E}}}_{{\boldsymbol{g}}}}^{{\boldsymbol{dir}}}$ - 2.623 eV) in Emidmidb polarization is formed by direct allowed transitions and in E⊥b polarization (2.698 eV) by forbidden transitions in Γ 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 , ε 1 and ε 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.