Structural, Optical, and Electrical Properties of ZnS Thin Films: Role of Cobalt Doping

The undoped and cobalt (Co) doped ZnS films were prepared by the spray pyrolysis technique. The doping concentration of the films was altered at 1 at%, 2 at%, 3 at%, and 5 at%, respectively. The prepared films exhibited a cubic phase with a prominent peak corresponding to the (111) plane. The crystallite size of the films varied from 5.2 to 8.7 nm with the addition of cobalt. The lattice constant of the films was slightly deviated from that of the undoped film. The bandgap of the films was reduced from 3.9 to 3.7 eV with the incorporation of the cobalt. The Urbach energy of the ZnS films was deviated from 0.44 to 1.11 eV with cobalt doping. The resistivity and carrier concentration of the films varied from 3.1 × 10 3 to 0.16 × 10 3 ohm cm and 0.22 × 10 15 to 2.27 × 10 15 cm −3 , respectively.