¹ Alshaab University,College of Health and Medical Technology, Medical Physics Department, Baghdad, Iraq.

² Ministry of Education/ General Directorate of Education Baghdad/ Karkh II, Baghdad, Iraq.

³ Department of Radiology Techniques, Dijlah University College, Baghdad, Iraq.

⁴ Department of physics, College of Education for Pure Science / Ibn Al-Haitham, University of Baghdad, Baghdad, Iraq.

* Correspondence: liqaasadiq20@gmail.com

Cobalt–chromium oxide thin films were deposited on glass substrates using the spray pyrolysis technique and subsequently annealed at 773 K for 60, 90, and 120 minutes. The influence of annealing time on the structural, morphological, and optical properties of the films was systematically investigated. X-ray diffraction analysis confirmed the formation of single-phase cubic spinel cobalt oxide (Co₃O₄) with Fd-3m symmetry. The crystallinity of the films improved with increasing annealing time, as indicated by enhanced peak intensity and reduced full width at half maximum. The crystallite size increased from 41.82 nm to 48.66 nm, accompanied by a decrease in microstrain and dislocation density, suggesting reduced structural defects. The absence of secondary chromium oxide phases indicates the possible incorporation of Cr³⁺ ions into the spinel lattice. Atomic force microscopy revealed grain growth and improved surface uniformity with increasing annealing time, consistent with XRD results. Optical analysis showed that the band gap varied from 2.0 eV (as-deposited) to 2.6 eV at 90 minutes, followed by a decrease to 2.2 eV at 120 minutes, attributed to defect reduction and structural evolution. These results demonstrate that annealing time plays a significant role in tailoring the physical properties of cobalt–chromium oxide thin films. The improvements in structural properties, defect reduction, and surface morphology contributed to enhanced material performance.