Effect of annealing atmosphere on physical characteristics and photoluminescence properties of nitrogen-implanted ZnO thin films

ZnO films were pre-treated with nitrogen implantation in the range from 5×1012 to 5×1015 cm−2. Effect of nitrogen concentration on structural crystallinity and photoluminescence properties of nitrogen-implanted ZnO films under different atmospheres and annealing treatments was investigated. It was found that there exists a solubility issue of nitrogen in ZnO films at 850 °C via secondary ion mass spectrometry (SIMS). It was found that the peak intensity of near band-edge (NBE) emission remarkably decreases with the increase of concentration of implanted nitrogen if annealed in nitrogen atmosphere due to the increased oxygen vacancies. However, when the ZnO was implanted with 5×1012 cm−2 and annealed in oxygen atmosphere, the optical properties are improved probably because the effective incorporation of O atom diminishes those donor levels (oxygen vacancies) and the crystallinity is also improved due to implanted nitrogen. However, excess nitrogen would reduce the crystallinity and promote the formation of the deep-level emission due to high amount of intrinsic and structure defects.