Effect of different annealing conditions on the properties of CdS thin films deposited by magnetron sputtering

CdS thin films were deposited on the substrate at temperature of 300 degree C by magnetron sputtering. The deposited films were annealed at temperature of 370 degree C, 380 degree C and 390 degree C, respectively, in either atmosphere of dry air or a mixture of CdCl(2) and dry air. The morphology, structure and optical properties before and after thermal annealing were investigated. The results show that for samples annealed in dry air, the variations of grain size, surface roughness and visible light transmittance with annealing temperature are not obvious, while the optical band gap increases with temperature increasing. Annealed in the mixture of CdCl(2) and dry air, recrystallization and grain growth in the samples are significant. Surface roughness increases with temperature increasing, on the contrary, visible light transmittance and optical band gap decreases. These phenomena are the results of changes in the temperature of recrystallization and doping concentration in the band tail states at different annealing atmosphere.