Characterization of new quaternary chalcogenide As-Ge-Se-Sb thin films

This paper reports the effect of replacement of selenium by antimony on the optical gap and some other physical parameters of new quaternary chalcogenide As14Ge14Se72-xSbx (where x = 3, 6, 9, 12 and 15 at%) thin films. Thin films with thickness 200-220 nm of As14Ge14Se72-xSbx were prepared by thermal evaporation of the bulk samples. Increasing antimony content was found to affect the average heat of atomization, the average coordination number, number of constraints and cohesive energy of the As14Ge14Se72-xSbx alloys. Optical absorption measurements showed that the fundamental absorption edge is a function of composition. Optical absorption is due to allowed, non-direct transition and the energy gap decreases with the increasing antimony content. The chemical bond approach has been applied successfully to interpret the decrease in the optical gap with increasing antimony content.