Investigating the optical, electronic, magnetic properties and DFT of NiO films prepared using RF sputtering with various argon pressures

Abstract

In this study, we investigated the structural, optical, magnetic, and conductive properties of nickel oxide (NiO) films on glass substrates deposited using Radio Frequency (RF) magnetron sputtering with varying Ar gas pressure and thickness. X-ray diffraction and Rietveld refinement analysis confirmed a cubic crystal structure and showed that the lattice parameters and the d(111)-space increased from 4.0559 Å to 4.2712 Å and from 2.3208 Å to 2.4582 Å, respectively, due to increased Ar pressure during deposition. Scanning electron microscopy and atomic force microscopy were used to determine the cross-sectional and surface topology of the NiO films, which exhibited uniform and homogeneous growth with an average spherical size of 54.28 ± 0.33 nm. The optical bandgap values of the films were calculated to be between 3.26 and 3.65 eV, increasing with pressure. Hall measurements confirmed the p-type semiconductor nature of the films with an average sheet carrier density of 1010 cm−2. The films exhibited soft magnetic properties, with a maximum Hc and Ms of 178.5 Oe and 5.82 emu/cm3 for 246 nm NiO film, respectively. Density functional theory (DFT) calculations confirmed the experimental results for both single to five layers NiO films and bulk NiO formations. The refined energy gap value was found to be 3.2 eV by the DFT calculation. The films produced at room temperature were found to be stable and reproducible, making them suitable as p-type materials for device construction.