Photoluminescence at the fundamental transition of thin (1.5 μm) CdS films formed by laser ablation on glass is investigated in the range 4-300 K. In contrast to previous studies on thin CdS films and crystals, the emission takes the form of a single peak over the whole temperature range centered at 487 and 500 nm at 4 and 300 K, respectively. By the application of the van Roosbroeck-Shockley relation and Urbach's rule, a direct relationship is shown between emission and absorption. It is further demonstrated that the LO phonon is found to form the Urbach tail and determines the temperature induced gap shift.
- thin films
- laser processing