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

Amorphous (As30Sb15Se55)(100-x)Te-x, (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 E-0 decreases while the width of localized states (Urbach energy) E-c increases by increasing Te content. The relationship between E-0 and chemical composition of the (AS(30)Sb(15)Se(55))(100-x)Te-x system were discussed in terms of Cohesive energy (CE), the average heat of atomization H-s, and the average coordination number N-r, The later are computed from the heat of atomization and the coordination number of used elements, respectively. (c) 2006 Elsevier B.V. All rights reserved.