Effect of Tl addition on the electrical properties of amorphous As20Se80-xTlx films

Thin films of As20Se80-xTlx; (5 <= x <= 35 at%) were prepared by thermal evaporation of the bulk materials. The effect of Tl addition on the electrical properties of As-Se-Tl chalcogenide semiconductors has been studied in the homogeneous glass-forming region through the low- and high-temperature range (173-373 K). The results indicated that the conduction in these glasses is through an activated process having two conduction mechanisms (band conduction in extended states and hopping conduction in localized states). The thallium in the As-Se-Tl ternary system tends to decrease the glass transition and melting temperatures and increase the DC conductivity in the amorphous phase. The activation energy for As20Se80-xTlx is found to vary between 0.9 and 0.64eV. A comparison between computed and measured densities was performed. The measured density appeared to be smaller than the computed one. This difference is attributed to the transformation of the material to the amorphous nature. (c) 2005 Elsevier B.V. All rights reserved.