TEMPERATURE-DEPENDENCE OF THE OPTICAL-ENERGY GAP AND THE THERMOELECTRIC STUDIES OF TLINS2 CRYSTALS

Single crystal of TlInS2 was prepared by a new crystal growth techniqu e. The interband absorption coefficients were measured near the fundam ental absorption edge as a function of the wavelength of the incident photons at various temperatures. The energy gap Delta E-g is temperatu re dependent and die absorption edge, shifts to lower energy values wi th increasing temperature. The energy gap, at room temperature has bee n found to be 2.24 eV. The dependence of the energy gap on temperature is linear in the temperature range 77-300 K with a negative temperatu re coefficient dE(g)/dT equal to 1.87X 10(-4) eV/K. A unique thermoele ctric phenomenon was observed. On the basis of two - band model the re sults have been discussed.