DOI: 10.11648/j.am.20261503.13 ISSN: 2327-252X

Growth Time-dependent Structural and Optical Properties of Hydrothermally Synthesized ZnO Thin Films

Mazabalo Baneto, Jeanne Aklamanu, Alphonse Gboglo, Ognanmi Ako, Abdoul-Razak Ali-Tagba, Monneka Kouide, Danoka Djagbai, Makadatièna Badjemna, Akotchayé Amenou
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The present study investigates the influence of growth time on the physical properties of ZnO thin films grown by the hydrothermal method. Film fabrication is carried out via a two-step process involving the deposition of ZnO seed layers on glass substrates by spin coating, followed by hydrothermal growth. Post-deposition annealing at 400°C for 3 hours is performed to enhance crystallinity. Structural and optical properties are analyzed using X-ray diffraction (XRD), UV–visible spectroscopy, and photoluminescence (PL) spectroscopy. XRD results confirm that all films are polycrystalline with a hexagonal wurtzite structure and exhibit a pronounced preferential orientation along the (002) plane. The progressive increase in the (002) peak intensity with growth time indicates enhanced crystalline quality, accompanied by an increase in crystallite size from 11.19 to 14.67 nm. UV–visible analysis shows that transmittance decreases from 95% to 65% with increasing growth time, mainly due to increased film thickness and density. However, films grown between 2 and 5 hours provide a good compromise between high transmittance in the visible region and strong absorption in the ultraviolet region. The optical bandgap varies from 3.14 eV to 3.27 eV, attributed to changes in film thickness. PL spectra exhibit three emission bands centered at 412 nm (3.01 eV), 438 nm (2.83 eV), and 490 nm (2.53 eV), associated with intrinsic defects in ZnO. The films grown for 4 hours exhibit relatively low defect density and good visible transmittance, making them promising candidates for photovoltaic applications.

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