Luminescence properties of ZnO and ZnO: Eu³⁺ nanostructures and thin films

Eu3+ doped ZnO thin films and ZnO nanorods were successfully prepared by using different techniques. Successful incorporation of Eu3+ ions in the ZnO matrix and preferred orientation along the c-axis for the films and the nanorods were achieved. The structure, morphology, luminescence and stability of the samples under electron beam irradiation were investigated. Firstly: Low Eu3+ concentration (0.4, 0.6, 0.8, and 1 mol%) doped ZnO thin films were successfully prepared using the spin coating technique. The preferred orientation of the films was reduced with increasing Eu3+ content. The average particle sizes and the optical band gap of the films decreased with increasing Eu3+ concentration. The films were excited at 325 nm and 464 nm using a xenon lamp. Upon excitation at 325 nm, the films exhibited band to band emission at ~378 nm and a broad deep level emission due to defects, with a small peak associated with characteristic Eu3+ emission at 614 nm that protruded from the broad band deep level emission. Upon excitation at 464 nm the characteristic Eu3+ emission features were observed and their intensity increased with increasing Eu3+ content until 0.6 mol% of Eu3+ and was then quenched. Multipole-multipole interaction, defects created due to the differences in ionic radii and charge states of Eu3+ and Zn2+ were found to contribute to luminescence quenching. Judd-Ofelt intensity parameters and asymmetry ratio analysis revealed the dependence of the Eu3+ emission intensity on the local environment around the Eu3+ ions in the host. Secondly: ZnO thin films doped with higher Eu3+ concentration up to 4 mol% were also successfully prepared using a sol-gel spin coating technique. X-ray photoelectron spectroscopy (XPS) confirmed the presence of Zn atoms in their doubly ionized state (Zn2+), while Eu atoms were found to be present in their divalent (Eu2+) and trivalent (Eu3+) states. Excitation spectra showed a broad band near 288 nm which was attributed to the charge tran
African Laser Centre (ALC)
National Laser Centre (NLC)