Electrical conductivity and dielectric properties of TlInS₂ single crystals

Department of Physics, Faculty of Education, Ain Shams University, Roxy, 11757 Cairo, Egypt

^a e-mail: hend2061@yahoo.com

Received: 13 December 2010
Revised: 4 February 2011
Accepted: 16 February 2011
Published online: 21 July 2011

Abstract

TlInS₂ single crystals were grown by using Bridgman-Stockbauer technique. Measurements of DC conductivity were carried out in parallel (σ_//) and perpendicular (σ_⊥) directions to the c-axis over a temperature range from 303 to 463 K. The anisotropic behaviour of the electrical conductivity was also detected. AC conductivity and dielectric measurements were studied as a function of both frequency (10²–10⁶ Hz) and temperature (297–375 K). The frequency dependence of the AC conductivity revealed that σ_ac(ω) obeys the universal law: σ_ac(ω) = Aω^s. The mechanism of the ac charge transport across the layers of TlInS₂ single crystals was referred to the hopping over localized states near the Fermi level in the frequency range >3.5 × 10³ Hz. The temperature dependence of σ_ac(ω) for TlInS₂ showed that σ_ac is thermally activated process. Both of ϵ₁ and ϵ₂ decrease by increasing frequency and increase by increasing temperature. Some parameters were calculated as: the density of localized states near the Fermi level N_F = 1.5 × 10²⁰ eV^-1 cm^-3, the average time of charge carrier hoping between localized states τ = 3.79 μs and the average hopping distance R = 6.07 nm.