Synergistic structural, optical, electronic, and magnetic tuning of NiO nanostructured thin films via 5.6 MeV Si2+ ion irradiation

NiO nanostructured thin films were deposited on glass substrates using the spray pyrolysis technique. The synthesized films were irradiated with 5.6 MeV Si 2+ ions at varying fluences of 2 × 10 13 , 1 × 10 14 , 2 × 10 14 , 1 × 10 15 , 5 × 10 15 ions/cm 2 . The effect of Si 2+ ion irradiation on the physical properties of NiO nanostructured thin films was systematically investigated. The average crystallite size of NiO decreased gradually from 17.28 nm to 11.45 nm at the highest fluence of 5 × 10 15 ions/cm 2 . Rietveld refinement revealed a slight increase in the goodness of fit (χ 2 ) with increasing fluence, indicating enhanced lattice disorder induced by ion irradiation. A reduction in optical transmittance was observed with increasing irradiation fluence, suggesting improved absorption due to irradiation-induced defect states and increased carrier concentration within the NiO lattice. The energy band gap of Si 2+ ion irradiated NiO decreased with increasing fluence, whereas the refractive index increased upon irradiation. Electrical measurements demonstrated a significant improvement in electrical conductivity accompanied by enhanced carrier mobility resulting from defect generation. These results demonstrate that Si 2+ ion irradiation is an effective method for tailoring the material properties of NiO thin films for potential applications in advanced optoelectronic and sensing devices.