Synthesis and Characterization of Mg–Co Co-Doped ZnO Thin Films via Spray Pyrolysis for Optoelectronic Applications

Abstract

This study investigates the synthesis and characterization of pure, magnesium-doped (MZO), cobalt-doped (CZO), and Mg–Co co-doped (MCZO) zinc oxide (ZnO) thin films deposited on glass substrates via a cost-effective spray pyrolysis technique. The research aims to evaluate the structural, morphological, and optical enhancements induced by single and co-doping to optimize ZnO for advanced optoelectronic applications. X-ray diffraction (XRD) analysis confirmed that all synthesized films possess a highly crystalline hexagonal wurtzite structure. Notably, the introduction of Mg and Co dopants significantly improved crystallinity, increasing the crystallite size from approximately 18.5 nm in pure ZnO to roughly 30 nm in the co-doped samples. Scanning electron microscopy (SEM) revealed a profound morphological transformation; while pure ZnO exhibited a porous, loosely agglomerated surface, the doped films demonstrated a highly compact, dense, and homogeneous microstructure with well-developed spherical grains. Optical properties, assessed through UV-Vis spectroscopy, showed that all films maintain high transparency in the visible spectrum. The optical band gap widened from 3.21 eV for pure ZnO to 3.26 eV for the MCZO thin films. Furthermore, the Urbach energy significantly decreased from 179 to 99 meV in the co-doped sample, indicating a substantial reduction in structural defects and lattice disorder. Consequently, the synergistic effects of Mg and Co co-doping considerably enhance the structural integrity and optical performance of ZnO thin films, demonstrating their strong potential for high-efficiency optoelectronic devices.