Characteristics of spray-deposited CdSe thin films

Cadmium selenide thin films were prepared for the first time by the chemical spray-deposition technique using non-toxic selenosulfate as the selenium source. Cleaned glass, conducting glass and metallic substrates were used. The substrate temperature was varied in the range from 300 to 500°C. The films were characterized by X-ray diffraction (XRD), optical absorption and photoconductivity measurements. XRD patterns indicated the presence of single-phase hexagonal CdSe. The resistivity of the as-deposited films was found to vary in the range 10–120 MΩ depending on the substrate temperature. A direct bandgap of 1.65 eV was obtained from optical absorption and spectral response measurements. A photosensitivity value of 3500 was obtained for the films deposited at a substrate temperature of 450°C.