Complex dielectric permittivity and electrical conductivity of (TlGaSe2)1–х (TlInS2)х solid solutions in an AC electric field

Abstract

We have synthesized the TlGaSe₂ and TlInS₂ compounds and (TlGaSe₂)_1–х (TlInS₂)_х (х = 0.2, 0.4) solid solutions. The phase composition of the (TlGaSe₂)_1–х (TlInS₂)_х (х = 0, 0.2, 0.4, 1.0) samples and crystals grown using these materials has been determined by X-ray diffraction. TlGaSe₂, TlInS₂, and the TlGaSe₂-based solid solutions (monoclinic crystal system) have been shown to be isostructural with each other. The dielectric properties of the grown crystals have been studied in ac electric fields at frequencies in the range f = 5 × 10⁴ to 3.5 × 10⁷ Hz. We have identified the relaxation nature of the dielectric permittivity of the crystals, the origin of the dielectric loss, and the hopping carrier transport mechanism in the samples. It has been shown that, with increasing x, the mean hop distance and time in the (TlGaSe2)_1–х (TlInS₂)_х solid solutions decrease, whereas the concentration of deep traps and the energy spread of the states localized in the band gap increase.