Effect of Te additions on the optical properties of (As–Sb–Se) thin films

Amorphous (As30Sb15Se55)100−xTex (with 0 ≤ x ≤ 12.5 at.%) were prepared by thermal evaporation. The optical transmission and reflection spectra of these films were measured in the wavelength range of 400–900 nm. The mechanism of the optical absorption follows the rule of allowed non-direct transition. It was found that, the optical band gab E0 decreases while the width of localized states (Urbach energy) Ec increases by increasing Te content. The relationship between E0 and chemical composition of the (As30Sb15Se55)100−xTex system were discussed in terms of Cohesive energy (CE), the average heat of atomization Hs, and the average coordination number Nr. The later are computed from the heat of atomization and the coordination number of used elements, respectively.