Abstract
In the present paper have investigated the effect of replacement of Te by Si on the optical gap and some other physical operating parameters of a quaternary chalcogenide As30Ge10Te60-xSix (where x = 0, 5, 10, 12 and 20 at %) thin films. Thin films with thickness 100-200 nm of As30Ge10Te60-xSix were prepared by thermal evaporation of the bulk samples. Increasing Si content was found to affect average heat of atomization, the average coordination number, number of constraints and cohesive energy of the As30Ge10Te60-xSix alloys. Optical absorption is due to allowed non-direct transition and the energy gap increases with increasing Si content. The chemical bond approach has been applied successfully to interpret the increase in the optical gap with increasing silicon content.