AC conductivity and dielectric properties of Sb 2Te 3 thin films

Abstract

Sb 2Te 3 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 2Te 3 films are amorphous while the source powder and annealed films showed a polycrystalline nature. The AC conductivity and dielectric properties of Sb 2Te 3 films have been investigated in the frequency range 0.4–100 kHz and temperature range 303–373 K. The AC conductivity σ AC( ω) was found to obey the power law ω s 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 1 and the dielectric loss ε 2 are frequency and temperature dependent and thickness independent. The maximum barrier height W M 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 AC, ε 1 and ε 2 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 2Te 3 films have been used to determined the molecular relaxation time τ. The temperature dependence of τ indicates a thermally activated process.