Luminescence of nanostructured Eu3+/ZnO mixed films prepared by electrodeposition

ZnO/Eu mixed. films have been prepared by electrochemical precipitation at an electrode surface. The films present a composite nanostructure with rod-shaped columns of EU3+-doped ZnO surrounded by a Eu/ZnO mixed basal layer. The fraction of basal layer increases rapidly with europium concentration in the deposition bath. The contribution of each component on layer photoluminescence has been distinguished by studying separately rod-rich and basal-layer-rich films. The films have been studied before and after annealing treatments in various atmospheres. Under UV light excitation, two photoluminescent ZnO emissions are observed: the exciton emission in the UV and a visible emission which is cancelled after a heating treatment at 400 degrees C in air. The sharp 4f-4f transition emissions of Eu3+ can be directly excited at 464 nm and are intense after an annealing treatment at 400 or 800 degrees C in air. A lifetime of 450 mu s is measured for the D-5(0) emitting level. EU3+ emission is also observed under ZnO excitation below 380 nm, but after film annealing, when defect effects are minimized.