Optical properties of annealing induced post growth ZnO:ZnFe2O4 nanocomposites

The effects of annealing on structural and optical properties of Fe doped ZnO nanoparticles have been investigated. XRD analysis reveals that prepared particles are in hexagonal wurtzite structure and formation of secondary phases which are related to the ZnFe2O4 phases. FTIR analysis confirms the wurtzite structure and the presence of Zn–O and Fe–O bonds. UV–visible measurements show free exciton absorption band appeared at 363 nm and red shifted for annealed samples. Room temperature photoluminescence spectrum of the as prepared Fe doped ZnO nanoparticles shows three bands which belongs to the near band edge emission (NBE) at 375 nm, blue emission at 450 nm and green emission at 556 nm. Annealed samples exhibit suppression of green emission band and red shift in the NBE emission band. This is attributed to the decrease in the oxygen vacancies and combined effects of size and exchange interaction between the conduction band electrons of ZnO and localised 3d electrons of the substitutional Fe ions, respectively.

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► Annealing induced optical properties of ZnFe2O4 nanocomposites were investigated.
► XRD analysis reveal increase in crystallite size with respect to annealing.
► UV–visible spectra show the red shift in the exciton absorption band with annealing.
► Red shift was explained under the week confinement regime.
► Annealing induced reduction in the band gap from 3.31 to 3.18 eV was observed.