Dielectric and optical properties of TlGa1 − x Er x S2 (x = 0, 0.001, 0.005, 0.01) single crystals

TlGa1 - x Er x S2 (x = 0, 0.001, 0.005, 0.01) solid solutions, based on the layered compound TlGaS2, have been prepared by direct elemental synthesis. The effect of Er concentration on the dielectric and optical properties of the TlGa1 - x Er x S2 solid solutions has been studied. The results demonstrate that increasing the Er content of the TlGa1 - x Er x S2 solid solutions decreases the real part of their complex dielectric permittivity and increases their dielectric loss tangent. The conductivity (I) of the TlGa1 - x Er x S2 solid solutions in the frequency range f = 1 to 35 MHz exhibits alpha similar to f 0.8 behavior, indicative of hopping charge transport through their band gap. We have evaluated the key parameters of this charge transport mechanism. We have studied temperature-dependent optical properties of the TlGa1 - x Er x S2 solid solutions. At temperatures in the range T = 77a200 K, the TlGa0.999Er0.001S2 solid solution has an absorption band near its fundamental absorption edge, which is due to transitions to a direct exciton state.