OPTICAL-PROPERTIES OF THE AS-GE-SE CHALCOGENIDE GLASS SYSTEM

The influence of composition and film thickness on the optical band ga p (E-g) and the width of the band tail (E-t) of thin solid films of ch alcogenide glass system As-Ge-Se were investigated. This was done by a n analysis of transmittance (T) and reflectance (R) spectra in the fun damental absorption region. It was found that the magnitude of E, decr eases with increasing Se content. The results were interpreted in term s of the change of cohesive energy (CE) as a function of Se content. T he cohesive energy was estimated by employing the chemical bond approa ch. It was also found that the increase of Se content is associated wi th an increase in the width of the band tails. The effect of him thick ness on E-g and E-t is discussed. (C) 1998 Elsevier Science Ltd. All r ights reserved.