Pre-exponential factor in a-Se75In25-xPbx thin films

Temperature dependence of d.c. conductivity is studied in a-Se(75)ln(25-x)Pb(x), thin films where x is varied from 0-10. From these measurements, the values of the pre-exponential factor (sigma(0)) and activation energy (DeltaE) are calculated for each glassy alloy. An approximate linear dependence of In sigma(0) on AE is observed in this glassy system with good agreement between the expected and calculated sigma(0) values using Meyer-Neldel rule. Linear dependence of ln sigma(0) on DeltaE in case of amorphous materials indicates that the conduction band tails a finite energy-distance towards the valence band and Fermi level is controlled by fixed dominant hole levels deeper in the gap.