The CBH model applied to a.c. conductivity measurements at microwave frequencies for As₂Se₃

Abstract

This paper reports measurements of the dielectric constant, dielectric loss and a.c. conductivity (σ_a.c.) for bulk samples of As₂Se₃ at different temperatures and frequencies ranging from 8 to 12 GHz. The study offers some new results to support the validity of the correlated barrier hopping (CBH) model for a.c. conduction in the microwave range. Our measurements provide explicit evidence to show that σ_a.c. saturates at 8 GHz, and a conversion of some of the bipolaron states into single-polaron states possibly takes place at higher temperatures. An attempt has also been made to calculate the hopping distance R and the mean intersite separation R _s, to check whether the magnitude of R is not only smaller but also comparable to the magnitude of R _s, because the CBH model assumes that the hopping of carriers remains confined to within a pair of sites.