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21 October 2004 Photo-induced changes of the optical constants of chalcodenide Ge19Sb1Te80 films
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Proceedings Volume 5581, ROMOPTO 2003: Seventh Conference on Optics; (2004) https://doi.org/10.1117/12.583032
Event: ROMOPTO 2003: Seventh Conference on Optics, 2003, Constanta, Romania
Abstract
In this work a preliminary study of the influence of light illumination on the optical constants of chalcogenide thin films with non-stoichiometric Ge19Sb1Te80 composition is presented. Films of Ge19Sb1Te80 with a thickness of ~1 μm were deposited onto glass substrates by vacuum thermal evaporation of parent glasses. The as-deposited films were exposed to light by using a 500 W HBO mercury lamp. The optical constants of the films, before and after their illumination, were evaluated from the ellipsometric measurements in the spectral range of 300 - 820 nm. It has been established that illumination of the films leads to a decrease of the refractive index in the studied spectral region, while a slight increase of the extinction coefficient in the 600 - 800 nm range is observed. For the given film composition the optical bandgap energy of 0.76 eV reduces to 0.62 eV. The film structure shows a very slow recovery expresed in the increase of bandgap energy towards its initial value. The observed decrease of the bandgap energy after illumination is indicative that the film structure undergoes rearrangements upon exposure to light leading to the effect of photodarkening.
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Vesela Pamukchieva, Anna M. Szekeres, and Kalina Todorova "Photo-induced changes of the optical constants of chalcodenide Ge19Sb1Te80 films", Proc. SPIE 5581, ROMOPTO 2003: Seventh Conference on Optics, (21 October 2004); https://doi.org/10.1117/12.583032
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