Characterization of chemical bath deposited CdS thin films at different deposition temperature

CdS thin films were deposited onto glass substrates by the chemical bath deposition (CBD). The influence of the deposition temperature varied from 55 °C to 85 °C in a step of 5 °C on the crystallographic structure, morphology as well as optical and electrical properties was investigated in detail. Increasing deposition temperature can promote phase transformation from cubic to hexagonal and improvement of crystallinity in CdS films. CdS film deposited at 75 °C shows compact and smooth surface, and excellent transmission in visible light range. The band gaps are found to decrease from 2.56 eV to 2.38 eV with the increase of deposition temperature, and the sub-band gap of about 2.32 eV is noticed at low deposition temperature of 55–70 °C. All CdS films are of n-type conductivity and the carrier concentration is in the order of 1012–1013 cm−3. The lowest resistivity and highest mobility obtained are in the case of 85 °C.