Structural and optical properties of thermally evaporated Sb doped Ge-Se thin films

Ge25Se75−xSbx chalcogenide thin films have been prepared by thermal vacuum evaporation technique with thickness 400 nm on glass/Si wafer substrates. The effects of composition, thermal annealing near glass transition temperature and laser-irradiation on the optical band gap and structural properties of these thin films were investigated. The glass transition temperature of Ge25Se75−xSbx chalcogenide glass was measured by non-isothermal Differential Scanning Calorimetric measurements. The influence of Sb content in Ge25Se75−xSbx system results in a gradual decrease in indirect optical gap from 1.86 to 1.43 eV, this behavior can be explained as increased tailing. On increasing the annealing temperature and laser-irradiation time, the optical band gap also decreases gradually for the crystallized films; this behavior can be attributed to transformation from amorphous to crystalline and was explained in the light of dangling bond model. The effect of annealing/laser irradiation on the nature and degree of crystallization has been investigated by studying the structure using X-ray diffraction and scanning electron microscope.