Influence of cation substitution on electrical conductivity and optical absorption edge in Cu₇(Ge1–xSix)S₅I mixed crystals

Abstract

Electrical conductivity of Cu₇(Ge₁₋xSix)S₅I mixed crystals was measured in the frequency range 1.0x10⁶ –1.2x10⁹ Hz and in the temperature interval 100–300 K. The frequency and temperature behaviour of the electrical conductivity were analyzed. The optical absorption edge of Cu₇(Ge₁₋xSix)S₅I mixed crystals within the temperature range 77–300 K was studied. The compositional dependences of the electrical conductivity, activation energy, optical pseudogap and Urbach energy were obtained. The influence of Ge→Si cation substitution on the optical absorption processes in the Cu₇(Ge₁₋xSix)S₅I mixed crystals is investigated.