OPTICAL-PROPERTIES OF EVAPORATED GE20SE80-XTLX THIN-FILMS

Chalcogenide glasses with composition Ge20Se80-xTlx (x = 10, 15, 20, 2 5, 35 %) have been prepared by the usual melt-quenching technique. Thi n films of the mentioned compositions have been prepared by the electr on beam evaporation. In addition, another set taken from the compositi on of X = 30 at % with different thicknesses (d = 14.7, 30.0, 56.5, 70 .0, 101.0, 180.0 nm) have been taken into consideration. The X-ray dif fraction (XRD) analysis revealed the amorphous nature of the prepared films. It was found that, in contrast to the optical gap (E(op)), both the extent of the band tailing (B), and the band gap (E(e)) increase with increasing thallium content. In other side, E(op) showed thicknes s independency. The refractive index (n) showed obvious dependence on both composition and thickness also on the energy of the incident radi ation.