Optimization of the synthesis and characterizations of chemical bath deposited Cu2S thin films

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.

Cuprous or cupric? How substrate polarity can select for different phases of copper sulfide films in chemical bath deposition

Copper sulfides have many applications from thermoelectrics to biotechnology. While the properties of different copper sulfide phases are well understood, controlling the deposited copper sulfide stoichiometry remains a significant challenge, especially in solution-phase synthesis techniques. In this work, we investigate the chemical bath deposition of Cu_xS on functionalized self-assembled monolayers (SAMs). Time-of-flight mass spectrometry, Raman spectroscopy, and x-ray photoelectron spectroscopy are employed to analyze the deposited films. We show that the use of thiourea as a sulfur source leads to the deposition of different copper sulfide phases and is controlled by the interaction of sulfur-containing ions in solution with the functionalized SAMs. For -COOH terminated SAMs, copper sulfide deposition is controlled by the surface polarity of the substrate. At the bath pH used in these experiments, the -COOH terminal groups are deprotonated. The resulting -COO^- terminated SAM surface repels negatively charged sulfur-containing ions, leading to the deposition of Cu₂S. For -CH₃ terminated SAMs, which are non-polar, there is no specific interaction between the SAM terminal group and sulfur-containing ions and CuS is deposited. For -OH terminated SAMs, which have a polar terminal group, there are two competing effects: the repulsion of S-containing ions by the small negative charge of the terminal -OH group and the increase in the concentration of sulfur-containing ions in solution as the bath pH increases. This competition leads to the deposit stoichiometry changing from Cu₂S at pH 9 to CuS at pH 12.