Photoluminescence properties of thin CdS films on glass formed by laser ablation

Photoluminescence at the fundamental transition of thin (1.5 mu m) CdS film s formed by laser ablation on glass is investigated in the range 4-300 K. I n 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 v an 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. (C) 1999 Elsevier Science Ltd. All rights reserved.