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Science Foundation in China

Photo-induced optical changes in GexAs40Se60?x thin films
Rashmi CHAUHAN1, Amit Kumar SRIVASTAVA2, Arvind TRIPATHI3, Krishna Kant SRIVASTAVA4
1. Department of Physic, DAV College, Kanpur 208001, India; 2. Material Science Programme, IIT Kanpur 208016, India; 3. Epsilonium Systems, Commercial Complex, Chunniganj, Kanpur 208001, India; 4. Department of Physics, DBS College, Kanpur 208006, India
Abstract:  Ge-As-Se chalcogenide thin films show a wide range of photosensitivity, which is utilized for the fabrication of micro-optical elements for integrated optics. The photosensitivity of GexAs40Se60?x (x=0, 15) chalcogenide thin films for UV light was presented. For that purpose, the bulk samples of GexAs40Se60?x (x=0, 15) chalcogenide glasses were prepared using conventional melt quenching technique, and thin films were prepared using thermal evaporation technique. These thin films were exposed to UV light for two hours. Amorphous natures of bulk samples and thin films were verified by XRD and chemical compositions were verified by EDX measurements. The thicknesses of the thin films were measured using a thickness profilometer. Linear optical analysis of these thin films was done using transmission spectra in wavelength range of 300?900 nm. Optical bandgap was determined by first peak of transmission derivative as well as extrapolation of Tauc’s plot. R2 analysis was done using R software to ensure that the material is indirect bandgap material. It is observed that two hours UV exposure causes photo-darkening along with photo-expansion in As40Se60 thin films, while photo-bleaching and photo-densification for Ge15As40Se45 thin films. However, the amounts of photo-induced optical changes for Ge15As40Se45 thin films are smaller than those for As40Se60 thin films. The changes in optical absorption, bandgap and thickness are understood based on the bonding rearrangement caused by UV exposure.
Keywords:  chalcogenide glasses; thin films; optical properties; photo-induced effect; optical band gap; UV exposure; R software
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