Structural, absorption, dispersion and photo-induced characteristics of thermally vacuum-evaporated BiSbSe3 thin films

• Photo-induced properties of BiSbSe3 are reported and depend on exposure time.
• Allowed Egind decreases with increasing light exposure time.
• Dispersion characterization of n was analyzed by Wemple–DiDomenico model.

Ternary chalcogenide glasses of BiSbSe3 were synthesized by a conventional direct fusion technique. X-ray diffraction, transmission electron microscopy and scanning electron microscopy were used for structural and morphology characterization. Polycrystalline and amorphous nature were examined by X-ray diffraction for powder and thin films of BiSbSe3, respectively. Thin films of BiSbSe3 were illuminated by incandescent white light using a 500 W tungsten lamp with different exposure times of 0.5, 1, 2, 23 h. During the illumination process, the ambient temperature was controlled at 303 K ± 1 by using temperature controller. Optical parameters such as, optical energy gap, refractive index, extinction coefficient, dielectric loss and dielectric tangent loss for the as-deposited and illuminated BiSbSe3 thin films were determined. Other important parameters such as dispersion energy, oscillating energy and the ratio between the free carrier concentrations to the effective mass were also investigated. Type of transition in BiSbSe3 films is indirectly allowed with a value of energy gap decrease with increasing illumination time. Decreasing in optical band gap of BiSbSe3 is explained on the basis of the change in nature of the films, from amorphous to nearly crystalline state, with increasing light exposure time.