Effect of Co60γ-irradiation on the optical properties of thin films from the system GeSe3–Sb2Se3–ZnSe

Abstract

Optical transmittance in the range from 200nm to 1100nm is measured for fresh and γ-irradiated thermally evaporated chalcogenide films of GeSe3, Sb2Se3, ZnSe, (GeSe3)80(Sb2Se3)20 and (GeSe3)70(Sb2Se3)10(ZnSe)20. The effect of ZnSe incorporation with both GeSe3, Sb2Se3 results in amorphous γ-radiation sensitive (GeSe3)70(Sb2Se3)10(ZnSe)20 composition as obtained from the estimated optical parameters. Optical energy gap, Eg, for (GeSe3)70(Sb2Se3)10(ZnSe)20 film shows a noticeable decrease from 1.81eV at 0kGy to 1.52eV at 690kGy and conversely the corresponding band tail width, Ee, increases from 0.123eV at 0kGy to 0.138eV at 690kGy. By contrast, the estimated values of Eg and Ee for (GeSe3)80(Sb2Se3)20 compositions, show no change with different γ-irradiation doses in the same range. The obtained results could be explained in terms of the band edge shift into the energy gap due to either the formation of localized states at the edges or weakening in the composition cohesive energy as reformation of new weaker bonds appear.