In the present work, we have deposited Se₈₀In₅Te₉Sn₆ thin films using the thermal evaporation technique under a vacuum of 10⁻⁶ Torr for phase change studies. The films were then irradiated with a Transverse Electrical Excitation at Atmospheric Pressure (TEA) nitrogen laser for varying exposure times. X-ray structural characterization indicated that the films are amorphous, whereas the laser-irradiated thin films exhibit a crystalline nature. Structural changes were further investigated using FESEM. The results are discussed with respect to structural aspects and the amorphous-to-crystalline phase transition. The observed changes are attributed to the interaction between incident photons and lone-pair electrons, which influence the band gap. The optical constants of the thin films were determined from absorption spectra as a function of photonic energy in the wavelength range of 400–900 nm, revealing a decrease in the optical band gap and an increase in the absorption coefficient with increasing laser irradiation time. The reduction in the optical band gap is attributed to the change in the film structure from an amorphous to a crystalline phase with increasing exposure time.
A. K. Srivastava (Wed,) studied this question.