The Influence of CBD Parameters on the Energy Gap of ZnS Narcissus-Like Nanostructured Thin Films

Surface topography, structural, optical and dc electrical behaviors of pristine and Co-doped ZnS thin films

The prime goal of the present research is to synthesize pristine zinc sulfide (PZS) and cobalt (Co)-doped zinc sulfide (CDZS) thin films with different doping concentrations (DC) via chemical bath deposition (CBD) method. The effect of Co-doping on the surface topography, structural, optical and dc-electrical behaviors of PZS thin films has been ascertained. Scanning electron microscopy images exhibited nearly sphere-shaped agglomerates of grains dispersed throughout the surface with cracks in PZS thin film whereas cracks were absent in CDZS. Atomic force microscopy image displayed smooth surface of CDZS thin film with evenly dispersed small grains. The hexagonal wurtzite structure of PZS and CDZS thin films with varied X-ray diffraction (XRD) parameters was confirmed via XRD analysis. Optical investigation revealed that the optical direct band gap energy increased with decreasing DC from 12 % to 4 %. Alteration of other optical parameters namely absorption coefficient, extinction coefficient, refractive index, real and imaginary parts of dielectric constant, etc. with DC was also discussed. Direct current electrical investigation revealed that the current-voltage characteristics are linear for all thin films signifying that the electrical conduction in CDZS is ohmic in nature.

The Effect of Deposition Parameters on Morphological and Optical Properties of Cu2S Thin Films Grown by Chemical Bath Deposition Technique

The chemical bath deposition technique has been used for the deposition of Cu2S thin films on glass substrates. The thickness of deposited thin films strongly depends on the deposition parameters. The present study revealed that the thickness increased from 185 to 281 nm as deposition time increased and from 183 to 291 nm as bath temperature increased. In addition, the thickness increased from 257 to 303 nm with the increment of precursors concentration and from 185 to 297 nm as the pH value increased. However, the thickness decreased from 299 to 234 nm with the increment of precursors concentration. The morphology of Cu2S thin films remarkably changed as the deposition parameters varied. The increase in deposition time, bath temperature, and CuSO4.5H2O concentration leads to the increase in particle sizes, homogeneity, compactness of the thin films, and the number of clusters, and agglomeration, while the increase in thiourea concentration leads to the decrease in particle sizes and quality of films. Optical results demonstrated that the transmission of thin films rapidly increased in the UV–VIS region at (λ = 350–500 nm) until it reached its maximum peak at (λ = 600–650 nm) in the visible region, then it decreased in the NIR region. The high absorption was obtained in the UV–VIS region at (λ = 350–500 nm) before it decreased to its minimum value in the visible region, and then increased in the NIR region. The energy bandgap of thin films effectively depends on the deposition parameters. It decreased with the increasing deposition time (3.01–2.95 eV), bath temperature (3.04–2.63 eV), CuSO4.5H2O concentration (3.1–2.6 eV), and pH value (3.14–2.75 eV), except for thiourea concentration, while it decreased with the increasing thiourea concentration (2.79–3.09 eV).

Annealing Effect on the Structure and Optical Properties of CBD-ZnS Thin Films for Windscreen Coating

Zinc sulfide (ZnS) thin films were prepared and synthesized by the chemical bath deposition (CBD) technique on microscopic glass substrates using stoichiometric amounts of the precursor materials (ZnSO₄·7H₂O, NH₄OH, and CS(NH₂)₂). Structural, morphological, compositional, and optical characterization of the films were studied. The obtained thin films were found to exhibit polycrystalline possessions. The effect of annealing temperature on the crystallographic structure and optical bandgap of ZnS thin films were both examined. The grain size and unit cell volume were both found to be increased. In addition, the strain, dislocation density, and the number of crystallites were found to be decreased with annealing temperature at 300 °C. However, the annealed sample was perceived to have more Zn content than S. The optical characterization reveals that the transmittance was around 76% of the as-deposited thin film and had been decreased to ~50% with the increasing of the annealing temperature. At the same time, the bandgap energy of the as-deposited film was 3.98 eV and was found to be decreased to 3.93 eV after annealing.