The role of annealing temperature on the optical energy gap and Urbach energy of Se:2%Sb thin films

The optical energy gap(Eopt) and the width of the tails of localized states in the band gap (ΔE) for Se:2%Sb thin films prepared by thermal co-evaporation method as a function of annealing temperature are studied in the photon energy range ( 1 to 5.4)eV.Se2%Sb film was found to be indirect transition with energy gap of (1.973,2.077, 2.096, 2.17) eV at annealing temperature (295,370,445,520)K respectively. The Eopt and ΔE of Se:2%Sb films as a function of annealing temperature showed an increase in Eopt and a decrease in ΔE with increasing the annealing temperature. This behavior may be related to structural defects and dangling bonds.