Cu-doped NiO thin films by ultrasonic spray pyrolysis: structural, optical, and electrical characterization

Undoped and Cu-doped nickel oxide (Cu:NiO) thin films were deposited on glass substrates by ultrasonic spray pyrolysis using Cu concentrations of 1, 2, 4, and 8 wt%. The influence of Cu incorporation on the structural, morphological, optical, Raman, photoluminescence, and temperature-dependent electrical properties of the films was systematically investigated. X-ray diffraction analysis confirmed the formation of polycrystalline cubic NiO with a preferred (111) orientation and no detectable secondary phases. The crystallite size increased at low Cu concentrations and decreased at higher doping levels because of defect-induced suppression of grain growth. SEM observations showed that Cu doping modified the surface morphology and grain distribution. The optical band gap decreased from 3.86 to 3.60 eV with increasing Cu content. Raman and photoluminescence analyses indicated that Cu incorporation altered the defect structure and increased non-radiative recombination. Temperature-dependent current–voltage measurements revealed typical negative temperature coefficient behavior, with conductivity increasing as both Cu concentration and temperature increased. These results demonstrated that controlled Cu doping effectively modified the structural, optical, and electrical properties of NiO thin films, making them promising materials for optoelectronic and sensing applications. © 2026 Elsevier Ltd and Techna Group S.r.l. All rights are reserved, including those for text and data mining, AI training, and similar technologies.