Growth and properties of CdS thin films deposited from aqueous solutions, using different cadmium salts

Cadmium sulphide (CdS) thin films were deposited on glass substrates using the homogeneous precipitation technique and different cadmium salts. The structure of the films was analysed using scanning electron microscopy (SEM). Thermally stimulated current (TSC) measurements had revealed the existence of several trapping levels in as deposited and annealed films. The activation energy of these traps was determined from TSC measurements. The following values were found for CdS films deposited from cadmium acetate: E1 = 0.3 eV; E2 = 0.45 eV, E3 = 0.51 eV. For CdS films deposited from cadmium chloride several trapping levels were found with the activation energies between 0.04 and 0.33 eV. A considerable enhancement of photoconduction after annealing in air was found. The experimental results were explained considering a sensitizing process due to the chemisorbtion of the oxygen.