Abstract
A study of the effect of the addition of Zn impurities on the electronic transport properties of melt-quenched semiconducting glasses in the system Se80-xTe20Znx (x = 0, 1, 2 and 4) has been undertaken for the first time. Measurements of the temperature dependence of the d.c. conductivity and the frequency and temperature dependence of the d.c. conductivity [sgrave]a.c.(ω) and dielectric relaxation have been made in the temperature interval 180–450 K and frequency range 500 Hz–10 kHz. It is revealed that [sgrave]a.c.(ω) is proportional to ω s . The temperature dependence of [sgrave]a.c.(ω) and the parameter s is reasonably interpreted by the correlated-barrier-hopping model. The analysis of the results shows that the electronic conduction in compositions with x = 0 and 1 takes place by a bipolaron-hopping process in the whole temperature range of study. The addition of higher concentrations of Zn impurities (x = 2 and 4) induces new types of defects which contribute predominantly to single-polaron-hopping at higher temperatures but the conduction at lower temperatures is of the bipolaron type. It seems that, at lower concentrations (x = 1 and 2) the Zn impurity cross-links the chains and ring structure of Se80Te20 and at higher concentrations (x = 4) it enters into the chains and rings.