AC conductivity and dielectric properties of amorphous Ge<inf>x</inf>Sb<inf>40-x</inf>Se<inf>60</inf> thin films

Abstract

Measurements of AC conductivity and dielectric properties have been made for chalcogenide film samples of GexSb40-xSe60 (with x=0, 10 and 20 at%) at different temperatures (303-393 K) and various frequencies (102-105 Hz). It was found that the AC conductivity obeys the law σ(ω, T)=Aωs. The exponent s<1 was found to decrease with increasing temperature through the entire range of temperatures and frequencies. This is interpreted by the correlated barrier hopping (CBH) model. Values of dielectric constant ε1 and dielectric loss ε2 were found to decrease with frequency and increase with temperature. The maximum barrier height WM was calculated from dielectric measurements according to the Guintini equation. It was found that the obtained value of Wm agrees with that proposed by the theory of hopping of charge carriers over potential barrier as suggested by Elliott in case of chalcogenide glasses. The density of localized states N(EF) has also been calculated for the studied compositions. The effect of decreasing the Sb content at the expense of the Ge content was investigated for the obtained results of the studied parameters. © 2008 Elsevier B.V. All rights reserved.