A comparative study of thermal annealing effects under various atmospheres on nano-structured CdS thin films prepared by CBD

• Smooth and uniform CdS thin films were deposited successfully by CBD method.
• The influence of CdCl2-assisted annealing under various atmospheres of CdS films has been investigated.
• We gave a more detailed research on annealing temperature after identified the most optimal annealing method.
• High quality CdS films were obtained with air–CdCl2-assisted treatments at 400 °C for 0.5 h.
• GIXRD was used as a new analysis method of CdS in this paper.

Cadmium sulfide (CdS) nanofilms have been deposited on the glass substrate using the chemical bath technique. The effects of CdCl2-assisted annealing under different atmosphere (vacuum, Ar and air) on the structural, morphological and optical properties of CdS nanofilms have been studied. After identifying the optimal annealing atmosphere, we also investigated the CdS thin film annealed at different annealing temperature (300, 400 and 500 °C). Films have been characterized by GI-XRD analysis, scanning electron microscopy, and UV–Vis–NIR spectrophotometer. The as-deposited CdS films have been found to be nanocrystalline in nature with a mixture of two crystallographic phases: a hexagonal phase and a cubic phase. After annealed in air with a CdCl2 coating layer at 400 °C, the films showed pure hexagonal phase, indicating the phase transition of CdS. It was found that the treatment in air with a CdCl2 coating layer increased the crystallinity and the mean grain size of CdS film, which are advantageous to the application in solar cells as a window layer material.