Abstract
The alternating-current (ac) conductivity and dielectric properties of Se85Te15-x Sb (x) (x = 0 at.%, 2 at.%, 4 at.%, and 6 at.%) films are reported in this work. Thin films were deposited by thermal evaporation under base pressure of 10(-5) Torr. The films were well characterized by x-ray diffraction, differential scanning calorimetry, and energy-dispersive x-ray spectroscopy. The ac conductivity and dielectric properties have been investigated for the studied films in the temperature range from 297 K to 333 K and over the frequency range from 10(2) Hz to 10(5) Hz. The experimental results indicate that the ac conductivity and the dielectric constant depend on temperature, frequency, and Sb content. The frequency dependence of was found to be linear with a slope lying very close to unity and is independent of temperature. This behavior can be explained in terms of correlated barrier hopping between centers forming intimate valence-alternation pairs. The density of localized states N(E (F)) at the Fermi level is estimated. The activation energy was found to decrease with increasing frequency. The dielectric constant epsilon (1) and dielectric loss epsilon (2) were found to decrease with increasing frequency and increased with increasing temperature over the ranges studied. The maximum barrier height W (m) for the studied films was calculated from an analysis of the dielectric loss epsilon (2) according to the Guintini equation. The values agree with that proposed by the theory of hopping of charge carriers over a potential barrier as suggested by Elliott for chalcogenide glasses. The variation of the studied properties with Sb content was also investigated.