Electrical properties of a-Se85−xTe15Snx thin films

Se–Te alloys are an important system of chalcogenide glasses from application point of view. The incorporation of Sn additive alters the electrical properties of these alloys. The conductivity measurements have been done on the thin films of a-Se85−xTe15Snx (x = 0, 2, 4, 6 and 10 at.%) deposited using vacuum evaporation technique. Both dark (σd) and photoconductivity (σph) show a maximum for x = 6 at.% of Sn, which, decreases on further Sn addition to the binary Se–Te alloy. The dark activation energy (ΔEd) shows a minimum for x = 2 at.% of Sn, but increases on further Sn addition. There is a sharp decrease in photosensitivity (σph/σd) on Sn addition to Se85Te15 alloy. The charge carrier concentration (nσ) calculated with the help of dc conductivity measurements also show a maximum at x = 6 at.% of Sn. The results are explained on the basis of increase in the density of localized states present in the mobility gap on Sn incorporation.