Chalcogenide glasses with composition Ge20Ses0_xTIx (x= 10, 15, 20, 25, 35%) have been
prepared by the usual melt-quenching technique. Thin films of the mentioned compositions
have been prepared by the electron beam evaporation. In addition, another set taken from
the composition 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 diffraction (XRD) analysis revealed
the amorphous nature of the prepared films. It was found that, in contrast to the optical gap
(Eop), both the extent of the band tailing (B), and the band gap (Ee) increase with increasing
thallium content. In other side, Eop showed thickness independency. The refractive index (n)
showed obvious dependence on both composition and thickness also on the energy of the
incident radiation.