Coexistence of photodarkening and photobleaching in Ge-Sb-Se thin films

• Published in: Journal of non-crystalline solids 2017-12, Vol.478, p.23-28
• Main Authors: Sati, Dinesh C., Jain, Himanshu
• Format: Article
• Language: English
• Subjects: Chalcogenide glass; Optical properties; Photo-bleaching; Photo-darkening; Photoinduced phenomena; Thin films
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2017.10.003

We have investigated photoinduced effects in as-deposited Ge40−xSbxSe60 (x=8, 15, and 20) films via in situ measurements of transmission spectra for wavelengths λ=500 to 950nm. The absorption coefficient increases initially, indicating the photodarkening (PD) effect, which rapidly saturates in tens of seconds. Then the absorption coefficient starts decreasing representing photobleaching (PB). The evolution of PD and PB can be described by stretched exponential function, yielding the time constants for the changes in absorption coefficients. The kinetics of PD is faster than that of PB. The coexistence of PB and PD suggests that the Sb and Ge based structural units of Ge-Sb-Se films respond to bandgap radiation independently. The structural origins of the observed opposing photoinduced effects are discussed. •First demonstration of coexistence of photodarkening and photobleaching in Sb-based chalcogenide glass films.•In situ measurements of photoinduced optical changes in chalcogenide glass films.•The kinetics of photodarkening is much faster than that of photobleaching.•The two phenomena have independent origins.•The atomistic mechanisms of the two phenomena are proposed.