ZINC OXIDE (ZnO) THIN FILMS SYNTHESIZED VIA COMBINED SPIN COATING AND CHEMICAL BATH DEPOSITION METHODS: THE INFLUENCE OF PRECURSOR CONCENTRATION ON THE PHYSICAL PROPERTIES

In this study, zinc oxide (ZnO) thin films were elaborated via a two-step process. The first step consisted of depositing a ZnO seed layer onto microscopic glass slide substrates using the spin-coating technique, with zinc acetate dihydrate as the precursor and ethanol as the solvent, at a precursor concentration of 0.01 M. The second step involved the growth of ZnO thin films by chemical bath deposition on the pre-seeded substrates, with the precursor concentration varied from 0.05 M to 0.30 M in increments of 0.05 M. The resulting thin films were subsequently annealed at 400 °C for 3 hours. The effect of precursor concentration on the structural and optical properties of the ZnO thin films was investigated using X-ray diffraction (XRD), UV-visible spectroscopy, and photoluminescence (PL) spectroscopy. The characterization results clearly reveal the significant influence of precursor concentration on the physical properties of the ZnO thin films.XRD analysis indicates that all synthesized films are polycrystalline and crystallize in a hexagonal wurtzite structure, exhibiting a preferential orientation along the (002) plane with increasing precursor concentration. UV-visible spectroscopy results show that all ZnO thin films are highly transparent, with transmittance exceeding 80 %. The optical band gap of the prepared films ranges from 3.18 eV to 3.25 eV. Photoluminescence spectra exhibit three emission peaks centered at approximately 390 nm (3.18 eV), 446 nm (2.78 eV), and 490 nm (2.53 eV). The dominant peak at 390 nm is attributed to free exciton recombination, corresponding to the direct band-to-band transition.