Photoluminescence and structural properties of cadmium sulphide thin films grown by different techniques

In this paper, we present a comparative study of photoluminescence and its relation to the structural properties of cadmium sulphide (CdS) thin films grown by chemical bath deposition (CBD), close spaced vapour transport, laser ablation (LA) and sputtering. Taking into account that the physical properties of CdS thin films depend upon the growth technique and the optimization of the deposition conditions for each technique, we show that the best crystal perfection occurs for LA-CdS films since the main photoluminescence peak at low temperature is due to bound excitons (2.53 eV). As expected, the films with the worst crystalline quality are those grown by CBD, ascertained by the photoluminescence band around 1.72 eV due to sulfur vacancies ('red band') without the corresponding exciton band. The photoluminescence results are correlated to x-ray diffraction measurements that confirm the above results.