In this study, undoped and silver (Ag)-doped nickel oxide (NiO) thin films were successfully grown by chemical spray pyrolysis (CSP) technique. XRD revealed that all films are polycrystalline, exhibiting a preferred orientation along the (200) plane. The crystallite size increased from 15.62 nm to 24.47 nm with increasing Ag content, accompanied by a reduction in microstrain and dislocation density, indicating improved crystallinity. Atomic force microscopy (AFM) images showed a decrease in average particle size from 78.3 nm to 41.1 nm and a reduction in surface roughness upon Ag doping, suggesting a more homogeneous, compact surface morphology. Optical transmittance measurements indicated a slight reduction in transparency from 72.8% to 68.9% with doping. The bandgap decreased from 3.56 eV to 3.43 eV. The refractive index and extinction coefficient decreased via Ag concentration, reflecting changes in the electronic polarizability and absorption behaviour. Gas-sensing measurements demonstrated that Ag doping significantly reduced the sensitivity to NH₃, with values decreasing from 48.96% for undoped NiO to 20.28% for 3% Ag-doped films at 300 ppm.
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