Thermal annealing induced structural, optical and electrical properties change in As40Se60-xBix chalcogenide thin films

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.