In present study the effect of excess sulfur on the optical absorption of chemically deposited CdS-Se thin films is observed. The optical absorption spectra shows a red shift in the on-set energy of direct band-to-band transitions and also in the band gap energy in films prepared with excess sulfur. The excitonic band edge absorption is identified in the optical absorption spectra. The XRD pattern of CdS-Se films prepared with excess sulfur shows predominance of cubic structure, where as that of films prepared without excess sulfur shows a hexagonal nature. The SEM studies also show different growth morphology in such films. All these changes could be related to the presence of excess sulfur in the lattice in the present study.
CdS-Se thin films, optical absorption, excitonic transitions
