Structural, surface and optical investigations of Cu⁺ implanted NiO film prepared by reactive sputtering

Nickel oxide (NiO) films were deposited on silicon substrate using a DC magnetron sputtering system. The deposited films were annealed at 400 °C for 2 h and then irradiated by 500 keV copper ions (Cu⁺) in the dose range of 1 × 10¹¹ to 1 × 10¹⁴ ions-cm⁻² using Pelletron Accelerator. X-ray diffraction study revealed NiO and Ni phases in the films corresponding to (111) and (200) planes. The lattice parameter was increased with the increase of ion dose to 1 × 10¹² ions-cm⁻² and then decreased at the higher doses. Ion irradiation at 1 × 10¹¹ ions-cm⁻² improved the crystallinity of the film while at the higher doses, the crystallinity was decreased. The surface morphology of the films showed a decrease in the compactness of the granular structure with increasing the ion dose. Fourier Transform Infrared spectroscopy showed Cu–O and Ni–O stretching vibration peaks in the irradiated films. X-ray photoelectron spectroscopy (XPS) results revealed a decrease in [Formula presented] and increase in the [Formula presented] ratio with an increase of the ion dose to 1 × 10¹² ions-cm⁻², demonstrating an increase in the Ni vacancies in the film at lower doses. The depth-resolved XPS analysis displayed a change in the Ni and O atomic percentages in the film with the increase of the etching time from 50 to 250 s and validated the existence of metallic Ni in the NiO film. The photoluminescence (PL) spectra analysis showed a decreasing trend in the band gap of the NiO film irradiated up to 1 × 10¹² ions-cm⁻², then an increasing trend at the higher doses.