EXCITONIC AND OTHER INTERBAND-TRANSITIONS IN TLINS2 SINGLE-CRYSTALS

A study of the optical properties of the layered compound TIInS2 is presented. Reflection spectra were measured at room temperature, in the energy region 1.5-6.2 eV. Transmission spectra were measured in the temperature range 10-290 K, in the energy region 1.5-3.5 eV. Two structures, at energy positions 2.58 and 2.87 eV (10 K), are attributed to transitions to ground exciton states, from valence states split because of the spin-orbit interaction, at the point Gamma of the Brillouin zone. Two other structures at higher energies are attributed to transitions at M(0) and M(3) critical points, respectively. The second-derivative spectra d(2) epsilon/d omega(2) were fitted, accordingly, to analytic two-dimensional critical-point line shapes. Lorentzian line shapes are used to fit the structures of excitonic origin. The temperature dependence of the peaks and their broadening parameters are also presented.