Kinetics of Ni-ZnO thin film growth on ITO: A study of nucleation and electrochemical deposition

In the present study, undoped and Nickel (Ni)-doped Zinc oxide (ZnO) thin films were deposited on indium tin oxide (ITO) substrates using a two-step electrodeposition technique. The deposition was performed at a potential of −1.21 V and a temperature of 70 °C for 60 min. Structural analysis by XRD confirmed a wurtzite phase with preferential (002) orientation. The crystallite size varied from 23.8 nm for pure ZnO to 22.4 nm at 6 mM Ni, indicating that Ni incorporation slightly refined the grain structure. Optical analysis revealed that the band gap increased from 3.88 eV to 3.93 eV (2 mM Ni), then decreased slightly to 3.85 eV (6 mM Ni) due to structural disorder and defect formation. SEM images showed well-aligned hexagonal nanorods with thicknesses ranging from 1.3 µm to 2.9 µm, confirming dense and uniform growth. These findings demonstrate that Ni doping influences both the nucleation mechanism and optical response of ZnO thin films, making them promising for optoelectronic and UV-sensing applications.