Role of heat treatment on structural and optical properties of thermally evaporated Ga10Se81Pb9 chalcogenide thin films

► Annealing effect on structure and optical band gap has been investigated. ► The amorphous nature has been verified by x-ray diffraction and DSC measurements. ► Thermal annealing causes a decrease in optical band gap in Ga10Se81Pb9 thin films. ► The decrease in optical band gap can be interpreted on the basis of amorphous-crystalline phase transformation. ► Optical absorption data showed that the rules of the non-direct transitions predominate.