Characterization of chemical bath deposited CdS thin films doped with methylene blue and Er

The optical, electrical, and structural properties of CdS thin films grown by chemical bath deposition and simultaneously doped with methylene blue (MB) and Er3+ were studied. Doping was achieved by adding a constant volume of an MB aqueous solution to the chemical bath while the relative volume (VR) of the Er aqueous solution varied within the range 0–10% of the total growing solution. X-ray diffractograms displayed the zincblende crystalline structure for all the CdS samples, with a remarked preferred orientation along the (111) direction. The interplanar distance among the (111) planes decreased for low doping leves of Er3+, while for high doping concentrations such distance increased to saturation. Measurements on the carriers density indicated that the CdS thin films doped with Er3+ at 6% VR presented the maximum value. In addition, the band gap energy (Eg) resulted higher for CdS:MB films with low Er3+ doping levels than for undoped films; however, Eg decreased until stabilization for increasing Er3+ concentrations