Conduction mechanism and the dielectric relaxation process of a-Se75Te25−xGax (x=0, 5, 10 and 15 at wt%) chalcogenide glasses

Abstract

Se75Te25−xGax (x=0, 5, 10 and 15atwt%) chalcogenide compositions were prepared by the well known melt quenching technique. Thin films with different thicknesses in the range (185–630nm) of the obtained compositions were deposited by thermal evaporation technique. X-ray diffraction patterns indicate that the amorphous nature of the obtained films. The ac conductivity and the dielectric properties of the studied films have been investigated in the frequency range (102–105Hz) and in the temperature range (293–333K). The ac conductivity was found to obey the power low ωs where s≤1 independent of film thickness. The temperature dependence of both ac conductivity and the exponent s can be well interpreted by the correlated barrier hopping (CBH) model. The experimental results of the dielectric constant ε1 and dielectric loss ε2 are frequency and temperature dependent. The maximum barrier height Wm calculated from the results of the dielectric loss according to the Guintini equation, and agrees with that proposed by the theory of hopping of charge carriers over a potential barrier as suggested by Elliott for chalcogenide glasses. The density of localized state was estimated for the studied film compositions. The variation of the studied properties with Ga content was also investigated. The correlation between the ac conduction and the dielectric properties were verified.