Effect of Cu incorporation on the crystallinity, lattice strain, morphology and electrical properties of nanostructured ZnS-PVA thin films

Highlights: • Cu incorporated ZnS-PVA thin films were synthesized by casting technique. • Lattice strain increases with increase of Cu concentration. • Elongated particles of average length ~ 650 nm were observed. • Transparency is enhanced due to incorporation of Cu. • The resistivity of the films is of the order of 108 Ωcm. Cu incorporated ZnS-PVA thin films at different concentration of Cu (0.5, 1, 5, 10 and 15% by volume) have been synthesized by solvent casting followed by thermolysis technique. X- Ray diffraction (XRD) studies revealed that the as-prepared thin films are nanocrystalline and possesses cubic phase with preferred orientation along (111) plane. The XRD peak intensity of the films decreases significantly at high Cu concentration. The lattice strain estimated through Williamson-Hall plot, increases with increase of Cu concentration. Scanning Electron Microscope images indicate homogeneous and continuous surface morphology of 5% Cu incorporated ZnS-PVA thin films. However, at high percentage of Cu the surface roughness increases with the formation of elongated shaped particles of average length ~650 nm. Optical band gap decreases from 3.72 to 2.80 eV with increase of Cu concentration. The room temperature electrical resistivity of the films is of the order of 10⁸ Ωcm.