Effect of 80-MeV nitrogen ion irradiation on ZnO nanoparticles: Mechanism of selective defect related radiative emission features

We report on the 80-MeV nitrogen ion irradiation on spherical ZnO nanoparticles fabricated by way of solid state mixing. The structural and compositional analyses of the as-synthesized ZnO nanoparticles were done by X-ray diffraction, electron microscopy and energy dispersive spectroscopy studies. As evident from the optical absorption spectra, the energetic ion irradiation, on the nanoparticle system, is governed by evolution of new characteristic absorption features owing to modification in the electronic states. Again, in the luminescence spectra, though the near band-edge emission was not observable for pristine ZnO, it was recovered (at ∼385 nm) upon irradiation. As far as the defect related emission is concerned, a competition between the formation and annihilation of different defects (especially, zinc vacancies and interstitials) at different ion fluences was realized. Correlating the luminescence spectra and the theoretical investigation, it can be understood that during irradiation the formation of zinc related defects are energetically favorable than the oxygen related counterparts. Exploration of defect related radiative features corresponding to definite structural organization/modification would help in making next generation light emitting and display devices, where a select emission response is desired.

Research highlights
► With an intention to study contribution of various defects to light emission process, solid state derived ZnO nanoparticles are irradiated with 80-MeV nitrogen ions.
► In the luminescence spectra, though the near band-edge emission was not observable for pristine ZnO, it was recovered (at ∼385 nm) upon irradiation.
► As far as the defect related emission is concerned, a competition between the formation and annihilation of different defects (especially, zinc vacancies and interstitials) at different ion fluences was realized.
► Correlating our experimental results and a model it was suggested that during irradiation the formation of zinc related defects are energetically favorable than their oxygen related defect counterparts.