Effects of laser irradiation on optical properties of a-Se_100−xTe_x thin films

Abstract

The effect of laser irradiation on the optical properties of thermally evaporated Se_100−x Te _x (x=8, 12, 16) chalcogenide thin films has been studied. The result shows that the irradiation causes a shift in the optical gap. The results have been analyzed on the basis of laser irradiation-induced defects in the film. The width of the tail of localized state in the band gap has been evaluated using the Urbach edge method. As the irradiation time increases, the values of the optical energy gap for all compositions decrease, while tail energy width increases. It is also observed that the optical energy gap decreases with increasing Te content in the alloy. These changes are a consequence of an increment in disorder produced by laser irradiation in the amorphous structure of thin film.

Keywords:

• chalcogenide glasses
• thin films
• irradiation effect
• optical properties
• order–disorder phenomena