Dielectric and optical properties of TlGa1 − xErxS2 (x = 0, 0.001, 0.005, 0.01) single crystals

TlGa 1 − x Er x S 2 ( x = 0, 0.001, 0.005, 0.01) solid solutions, based on the layered compound TlGaS 2 , have been prepared by direct elemental synthesis. The effect of Er concentration on the dielectric and optical properties of the TlGa 1 − x Er x S 2 solid solutions has been studied. The results demonstrate that increasing the Er content of the TlGa 1 − x Er x S 2 solid solutions decreases the real part of their complex dielectric permittivity and increases their dielectric loss tangent. The conductivity (σ) of the TlGa 1 − x Er x S 2 solid solutions in the frequency range f = 1 to 35 MHz exhibits σ ∼ 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 TlGa 1 − x Er x S 2 solid solutions. At temperatures in the range T = 77–200 K, the TlGa 0.999 Er 0.001 S 2 solid solution has an absorption band near its fundamental absorption edge, which is due to transitions to a direct exciton state.