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Amorphous chalcogenide semiconducting materials are very sensitive to electromagnetic radiation and are useful for infrared optics and play a pivotal role in modern technology. In the present article, As 2 Se 3 and bilayer Bi/As 2 Se 3 thin films were prepared by thermal evaporation method. The 532 nm laser induced diffusion of active Bi top layer into barrier As 2 Se 3 film was probed through spectroscopic techniques. An X-ray diffraction study reveals no structural change due to laser irradiation while the optical parameters are affected by both Bi addition and laser irradiation which brings a change in the transmittivity and absorption coefficient. The indirect optical band gap is found to be decreased by 0.11 eV due to Bi addition to As 2 Se 3 which is explained on the basis of density of defect states with an increase in disorder.The laser irradiated Bi diffusion increases the optical band gap by 0.05 eV (photobleaching) with a decrease in disorder. The Tauc parameter and Urbach energy which measures the degree of disorder change with Bi doping and irradiation. The refractive index is modified by the illumination process which is useful for optical applications. The optical property change is well supported by X-ray photoelectron core level spectra and Raman spectra.

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This work reports the formation of topological Bi2Se3 phase upon annealing higher % of Bi content in amorphous As40Se60-xBix (x = 2, 7, 10 and 15%) chalcogenide thin films prepared by thermal evaporation process. The phase identification was done by X-ray diffraction study and Field emission scanning electron microscopy studies confirm the phase transformation in As40Se45Bi15 thin film. The Raman measurements indicated the formation of crystalline As4Se4 and Bi2Se3 phase with annealing at 473K and the indirect optical band gap were found to decrease with increase in Bi concentration on thermal annealing as probed from the optical measurement. The changes in optical parameters were described on the basis of the density of localized states and the electrical resistance was found to be decreased which has been measured at room temperature by using the two-point probe technique.