X-ray excited optical luminescence studies of ZnO and Eu-doped ZnO nanostructures

Pure (ZnO) and Eu-doped ZnO (Eu:ZnO) nanostructures have been grown in different morphologies by thermal evaporation. The growth of the structures depends on the temperature and concentration gradient during material deposition as well as on the doping species. X-ray excited optical luminescence (XEOL) from nanostructured ZnO and Eu:ZnO shows a correlation of optical properties with morphology on a nanoscale. In particular, the relative intensity of band gap and defect emission (green light) changes drastically in Eu:ZnO and ZnO nanostructures with different morphology. In this Article, we present experimental results from Eu:ZnO and ZnO nanostructures, using synchrotron radiation-based XEOL, time-gated XEOL, and element specific XANES with partial and total photoluminescence yield (PLY). Our results suggest that the rare earth dopant most likely affects the energy transfer and structural changes by nucleation, rather than direct radiative decay from Eu sites.