Investigations on tailoring physical properties of RF magnetron sputtered Cadmium Sulphide thin films

The effect of nitrogen (N₂) partial pressure on the structure and bandgap tunability of RF magnetron sputtered Cadmium Sulphide (CdS) thin films is investigated by varying N₂ partial pressure in Ar/N₂ mixture. In presence of N₂, films have a polycrystalline structure with (0 0 2) preferential orientation, which leads to defect-free, continuous, dense, and fibrous structures with increased roughness. The average optical transmittance increased to > 80 at 500–2500 nm for 30 % N₂ partial pressure, whereas the band gap decreases from 2.45 eV to 2.30 eV with increasing N₂ concentration. This work shows that the bandgap of sputtered CdS thin films can be tuned with the variation of N₂ concentration for customized applications.