Assessment of the Optical and Structural Properties of Zinc Oxide Thin Films Prepared by Chemical Bath Deposition

Zinc oxide is a wide band gap semiconductor with extensive applications in thin film transistors, UV photodetectors, and dye-sensitised solar cells. Chemical bath deposition offers a low-cost, low-temperature route to ZnO film preparation suitable for Nigerian research institutions with limited infrastructure. This study investigates the optical and structural properties of ZnO thin films deposited by chemical bath deposition on glass substrates using zinc nitrate and hexamethylenetetramine precursors at temperatures of 70, 80, and 90 degrees Celsius and deposition times of 1, 2, and 4 hours. Film structure is characterised by X-ray diffraction, and optical transmittance and reflectance are measured from 300 to 800 nm by UV-Vis spectrophotometry. The optical band gap is determined by Tauc plot analysis. Surface morphology is characterised by scanning electron microscopy. Results indicate that films deposited at 90 degrees Celsius for 4 hours exhibit preferential c-axis orientation with narrow XRD peaks at 34.42 degrees corresponding to the ZnO (002) wurtzite reflection. The optical band gap narrows from 3.37 to 3.28 eV with increasing deposition time, consistent with improved crystallinity. Transmittance exceeds 80 percent in the visible region for all samples. Keywords: zinc oxide, thin film, chemical bath deposition, optical band gap, XRD