Studies of grain size effects in rf sputtered CdS thin films

Abstract

CdS thin films with various grain sizes were produced by rf sputtering and in situ postannealing processes. For a series of annealing time intervals, the average grain sizes of an as-deposited thin film with thickness ∼4000 Å were found to vary from ∼280 to ∼1500 Å. Three bands located in the green, yellow, and red regions were observed in photoluminescence (PL) spectra of these as-deposited films. The temperature dependence of (PL) spectra of CdS microcrystals was investigated. The variations of the (PL) spectra with average grain size and thickness of CdS thin films were also studied. It was found that the intensity of the yellow band was increased as increasing the film thickness while the intensity of the red band was decreased as the grain size of the film became larger. The peak positions of the yellow and red bands were found to be blue-shifted as the films became thinner.