Frequency effect on the electrical and dielectric properties of (TlGaS2) 1 − x(TlInSe2)x (x = 0.005, 0.02) single crystals

The electrical properties (loss tangent (tanδ), real (ɛ) and imaginary (ɛ″) parts of complex dielectric permittivity, and ac conductivity across the layers (σac)) of (TlGaS2)1 − x(TlInSe2)x (x = 0.005, 0.02) layered single crystals have been studied in the frequency range f = 5 × 104 to 3.5 × 107 Hz. The results demonstrate that the dielectric dispersion in the crystals has a relaxation nature. Almost throughout the frequency range studied, their ac conductivity follows the relation σac ∼ f0.8, characteristic of hopping conduction through localized states near the Fermi level. The Fermi-level density of states (NF), the spread of their energies, the mean hop time τ and distance R, and the concentration of deep traps determining the ac conductivity of the crystals (Nt) have been estimated. With increasing x in (TlGaS2)1 − x(TlInSe2) x, NF and Nt increase, while τ and R decrease.