Effect of Eu3+ on the structure, morphology and optical properties of flower-like ZnO synthesized using chemical bath deposition

The chemical bath deposition (CBD) method was used to synthesize ZnO undoped and Eu3+-doped nanostructures. The Eu3+ concentration was varied from 0.2 to 5 mol%. The X-ray diffraction (XRD) spectra of the undoped and low concentration Eu3+ doped ZnO nanostructures correspond to the various planes of a single hexagonal ZnO phase. The estimated crystalline grain size was calculated using the XRD spectra and was found to be in the order of 47±5 nm and independent on the Eu3+ ion concentration up to 4 mol%. Scanning electron microscopy (SEM) micrographs, however, indicate that the addition of Eu3+ influences the morphology of the samples. In the UV–vis study the highest band gap energy was obtained for the undoped ZnO. The effective band gap energy of the ZnO decayed exponentially with the addition of Eu3+ up to 4 mol% where impurity phases started to appear. Although weak luminescence was observed for excitation above the bandgap at 300 nm the best results were obtained by exciting the Eu3+ directly through the 7F0→5L6 absorption band at 395 nm. Excitation at a wavelength of 395 nm produced the highest Eu3+ luminescence intensity without any noticeable ZnO defect emissions. The maximum luminescence intensity for this excitation was obtained for ZnO:3 mol% Eu3+ ions and luminescent quenching was observed for higher Eu concentrations.