Effects of nitrogen and oxygen partial pressure on the structural and optical properties of ZnO:N thin films prepared by magnetron sputtering

Nitrogen doped ZnO films were prepared by magnetron sputtering. We studied the influence of nitrogen partial pressure pn and oxygen partial pressure po on the microstructure, morphology and optical properties of the thin films. The results show that different defects influence the structure and optical behavior of the films. Doping-related tensile stress turns compressive, owing to a different N-doping form in the films. Red-shift of absorption edge was observed with increasing pn and decreasing po. Band-gap narrowing is improved by increasing nitrogen substitute and oxygen vacancies. •ZnO:Nfilms were prepared with/without O2 pressure.•Microstructure, morphology, and optical properties of the films were investigated.•Different defects influence the structure and optical behavior of the films.•Band-gap is narrowed by increasing nitrogen substitute and oxygen vacancies.•N substitute, not N interstitial, is an effective factor narrowing band gap.