Properties of CdS thin films prepared by the spray pyrolysis technique

Cadmium sulphide thin films were prepared by the spray pyrolysis technique from solutions containing equimolar (0.1 M) cadmium chloride and thiourea ((NH2)2CS) on glass substrates, whose temperature was varied from 250 to 450 degree C. Pure CdS thin films with the hexagonal structure were formed above 300 degree C and the number of pinholes in films decreased as the substrate temperature increased. Optical transmittance of films deposited at 400 degree C was about 75% and the optical band gap of films was 2.43 eV regardless of the substrate temperature. Dark electrical resistivity of films deposited at 400 degree C was of the order of 105 Ω centre dot cm and all films exhibited high photoconductivity