TEMPERATURE AND COMPOSITION DEPENDENCE OF ELECTRICAL CONDUCTIVITY IN a-Se70Te30-xZnx THIN FILMS

In the present paper D.C. conductivity measurements have been made on Se70Te30-xZnx (x = 0, 2, 8) thin films in the temperature range 255-360K. Two regions have been observed in the entire temperature range. One such region is at low temperatures 255K to 305K and other region is in high temperature range 310K to 360K. In the high temperature range conductivity is thermally activated having single activation energy. Electrical parameters (activation energy (Delta E) and pre-exponential factors sigma(o)) have been calculated for each sample. It has been observed that the activation energy decreases on increasing concentration of Zn. Composition dependence of conductivity shows that conductivity decreases at 2% of Zn. However on further incorporation of Zn, conductivity increases. Same behavior has been observed for pre-exponential factor (sigma(o)). In low temperature range (255-305K) variable range hopping conduction is observed. Mott parameters and density of localized states near Fermi level have been calculated. Density of localized states decreases at 2% of Zn and then increases with the further increases in Zn concentration.