Abstract :
The optical gap (Eopl) and tailing(delta E) for Sc:2%As thin films prepared by vacuum evaporation as a function of annealing temperature are studied in the photon energy range (1,0 to 5.4 ) eV. Thin film of Se:2%As was found to be indirect gap with energy gap of (1.978 , 2.082 , 2.120 , 2.230) eV at annealing temperature (295 , 370 , 445 , 520)K respectively. The Eopt and delta E of Se:2%As films as a function of annealing temperature showed an increase in Eopt and a decrease in delta E with the temperature. This behavior may be related to structural defects and dangling bands. The absorption coefficient for Se:2%As films exhibits exponential dependence on photon energy obeying Urbach s rule in the absorption edge.
