Effect of CdCl2/annealing on the crystalline transformation of CdTe thin films grown by evaporation at a low substrate temperature

The structural and optical properties of CdTe thin films prepared at a low substrate temperature were investigated before and after the CdCl2/annealing. The crystal structure of CdTe film was cubic with a strong (111) preferential orientation. Annealing at 400 degrees C without CdCl2 treatment results in a decrease in the (111) peak intensity while the intensities of the (220), (311) and (331) peaks appeared, indicating that the texture is significantly changed. However, after the CdCl2/annealing, the film exhibited a hexagonal phase as a dominant structure. The scanning electron microscopy patterns showed that the as-deposited and annealed samples had almost the same grain size. However, the grain size of the sample annealed after the CdCl2 treatment increased significantly. The optical band gap values for the as grown and CdCl2/annealed films were determined to be similar to 1.48 eV and similar to 1.49 eV, respectively.