AC conductivity and dielectric properties of Sb<inf>2</inf>Te<inf>3</inf> thin films

Abstract

Sb Te films of different thicknesses, in the thickness range 300-620 nm, were prepared by thermal evaporation. X-ray analysis showed that the as-deposited Sb Te films are amorphous while the source powder and annealed films showed a polycrystalline nature. The AC conductivity and dielectric properties of Sb Te films have been investigated in the frequency range 0.4-100 kHz and temperature range 303-373 K. The AC conductivity σ (ω) was found to obey the power law ω where s≤1 independent of film thickness. The temperature dependence of both AC conductivity and the exponent s can be reasonably well interpreted by the correlated barrier hopping (CBH) model. The experimental results of the dielectric constant ε and the dielectric loss ε are frequency and temperature dependent and thickness independent. The maximum barrier height W calculated from dielectric measurements according to the Guintini equation agrees with that proposed by the theory of hopping of charge carriers over a potential barrier as suggested by Elliott for chalcogenide glasses. The effect of annealing at different temperatures on the AC conductivity and dielectric properties was also investigated. Values of σ , ε and ε were found to increase with annealing treatment due to the increase of the degree of ordering of the investigated films. The Cole-Cole plots for the as-deposited and annealed Sb Te films have been used to determined the molecular relaxation time τ. The temperature dependence of τ indicates a thermally activated process. © 2005 Published by Elsevier Ltd. 2 3 2 3 2 3 AC 1 2 M AC 1 2 2 3 s