Optoelectronic properties of p-type NiO films deposited by direct current magnetron sputtering versus high power impulse magnetron sputtering

High power impulse magnetron sputtering (HiPIMS) technology has attracted lots of attention due to its high target ionization rate. This characteristic is desirable in preparing metal compounds with complex valence states. In the current work, NiO films were deposited by HiPIMS and direct current magnetron sputtering (DCMS) at various oxygen flow ratios. The films’ structural and optoelectronic properties were investigated. The results show that, thanks to the enhanced Ni3+ ion density formed during the HiPIMS deposition process, more nickel vacancies are formed in the film leading to the film’s carrier concentration improving significantly. NiO films deposited by HiPIMS possess much better p-type conductivity than the films deposited by DCMS. Additionally, with oxygen flow ratio increase, more interstitial oxygen can be introduced, which can also enhance the film’s p-type electrical conductivity. However, these defects reduce the film’s transmittance.