(Co₃O₄: Cu) nanostructured films were deposited by the chemical spray pyrolysis (CSP) method. XRD analysis assure a polycrystalline cubic structure with peak at (220) plane. Improved crystalline quality was demonstrated by the crystallite size increasing from 16.96 nm for undoped films to 27.82 nm for 3% Cu-doped samples, and the dislocation density decreasing from 39.74 × 10¹² to 30.41 × 10¹² lines/m². Surface alteration was detected by AFM, and the average particle size decreased from 68.6 nm to 32.6 nm after dopingAs Cu content rose, optical transmittance in the visible range dropped from 85.5% to 80.6%, whereas absorbance steadily increased. Due to defect-state formation within the band structure, the direct optical bandgap decreased from 2.50 eV to 2.40 eV. Strong light absorption was confirmed by the absorption coefficient exceeding 10^cm⁻¹. Because of structural alterations, the refractive index dropped as the Cu content increased. Copper doping greatly affected sensor response, as seen by gas-sensing experiments for NO₂ at 80°C. Sensitivity dropped from 53.62% for undoped Co3O₄ to 29.43% for 3% Cu-doped films at 220 ppm, demonstrating decreased sensitivity at higher doping levels.
Keywords
Co₃O₄CuSPMStructural PropertiesOptical Band GapNO₂ Gas Sensing
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