CuO thin layers were synthesized using the sol–gel method and deposited onto glass substrates through the dip-coating technique. The impact of annealing temperatures on the structural, optical, and electrical characteristics of the developed CuO thin layers was comprehensively assessed through X-ray diffraction, UV–visible spectrophotometry, and four-point techniques, respectively. X-ray diffraction analysis revealed the formation of CuO thin layers with a distinctive monoclinic tenorite phase structure. The UV–visible spectrophotometer results demonstrated a decrease in transmittance from approximately 30% to about 7% as the annealing temperature increased from 200 °C to 400 °C. The semiconducting properties exhibited temperature-dependent variations, with the band gap narrowing from 1.70 to 1.48 eV as the temperature increased from 200 to 400 °C. Additionally, the electrical conductivity of the CuO layers exhibited a significant increase from 48 to 61 S.m−1 over the same temperature range. Collectively, the findings suggest that an annealing temperature of 400 °C is optimal for achieving well-crystallized CuO layers with desirable characteristics, including high absorbance, low transmittance, a reduced energy band gap, and enhanced electrical conductivity. These results underscore our ability to manipulate CuO properties, offering insights for tailoring them to meet specific requirements, particularly in the context of gas sensor applications.
Doubi et al. (Sun,) studied this question.