Ac conductivity and dielectric properties of Ge20Se75In5 films

Amorphous films of Ge20Se75In5 chalcogenide glass were prepared using a thermal evaporation technique. The chemical composition of the deposited films was examined using energy dispersive X-ray spectroscopy (EDX). The ac conductivity and dielectric properties of the prepared films have been studied as a function of temperature in the range from 300 to 423 K and frequency in the range from 102 to 105 Hz. The experimental results indicate that ac conductivity σac(ω) is proportional to ωs where s equals 0.902 at room temperature and decreases with increasing temperature. The results obtained are discussed in terms of the correlated barrier hopping (CBH) model. The density of localized states N(EF) at the Fermi level is found to have values of the order 1019 eV−1 cm−3, which increase with temperature. The dielectric constant ɛ1 and dielectric loss ɛ2 were found to decrease with increasing frequency and to increase with increasing temperature over the ranges studied. The maximum barrier height Wm was estimated from an analysis of the dielectric loss ɛ2 according to Giuntini equation. Its value for the deposited films (0.43 eV) agrees with that proposed by the theory of hopping of charge carrier over a potential barrier as suggested by Elliott for chalcogenide glasses.