Time dependent bond arrangement approach to photo-induced changes in Ge30-xSbxSe70 thin films

• Published in: Materials chemistry and physics 2020-02, Vol.242, p.1, Article 122521
• Main Authors: Abdel-Wahab, F., Ali Karar, N.N., Merazga, A.
• Format: Article
• Language: English
• Subjects: Blue shift; Chalcogenide; Composition; Doppler effect; Optical properties; Photobleaching; Photodarkening; Qualitative analysis; Red shift; Swanepoel's methods; Thin films; Time dependence
• ISSN: 0254-0584; 1879-3312
• DOI: 10.1016/j.matchemphys.2019.122521

The transmission spectra of thermal evaporation amorphous Ge30-xSbxSe70 (x = 0, 5, 10, 15) thin films measured before and after different time of light exposure. To determine the optical properties of these films, the data of the spectra have been analyzed by means of the Swanepoel's methods. The values of optical band gap (Eg) were deduced via Tauc extrapolation method. Either a red shift (photodarkening) and a blue shift (photobleaching) were observed in the investigated composition depending on the composition (x). The results are justified using a model in which, the variation of Eg in such chalcogenide films depends on the rates of bonds-breaking and reconstruction during illumination. The model reflects an excellent qualitative agreement with the experimental results. •Ge30-xSbx Se70 films at four compositions (x = 0, 5, 10 and 15) was prepared by thermal evaporation method.•Transition from photo-bleaching to photo-darkening occurs by increasing the value of x.•A simple phenomenological model, based on Manca's equation and the random covalent network model (RCNM), is introduced.•Qualitative explanation of the Eg variation with light exposure time is obtained.