Thickness dependence of structural, optical and electrical properties of NiO thin films grown by RF magnetron sputtering

Nickel oxide (NiO) thin films with varying thicknesses (5–100 nm) were deposited on fused silica at room temperature via RF magnetron sputtering in pure argon. Optimal deposition conditions were established by analyzing deposition rates under varying pressures (5–25 mTorr) and powers (75–250 W). Structural, optical, and electrical properties were studied using X-Ray Diffraction (XRD), Atomic Force Microscopy (AFM), UV–VIS spectroscopy, and I–V measurements. XRD confirmed a face-centered cubic structure, with a preferred orientation shift from (111) to (200) as thickness increased, and the appearance of the (220) peak beyond 20 nm. Crystallite size, microstrain, and dislocation density stabilized for films thicker than 20 nm. EDS analysis revealed uniform growth and an increasing Ni:O ratio with thickness, affecting transmittance and resistivity. A slight bandgap increase (3.52 to 3.54 eV) and a significant resistivity drop (to 3.0 × 10^–3 Ω m) were observed with increasing thickness, attributed to reduced oxygen concentration and improved film quality.