Determination Of D. C. Conduction Parameters In A-Se100-Xbix Thin Films

Temperature dependence of d. c. conductivity is studied in a-Se100-xBix thin films, where x is varied from 0.5 to 6 in the temperature range (255 K to 360 K). Two regions have been observed in the entire temperature range. The first region is in the temperature range (308 K-360 K) which is known as high temperature region and the second region is in the temperature range (255 K-305 K) which is low temperature region. The conductivity curve in the first region shows the exponential increase in conductivity with temperature having single activation energy. Electrical parameters have been calculated for each sample in this region. It has been observed that the activation energy decreases on increasing the concentration of Bi in a-Se100-xBix. Composition dependence of conductivity shows that conductivity first decreases with increase in Bi concentration and thereafter increases on increasing concentration of Bi. In low temperature range (II region), variable range hopping conduction is observed. Mott parameters and density of localized states near Fermi level have been calculated. The results indicate that the density of localized states increases on increasing concentration of Bi in a-Se100-xBix.