Electrodeposition and characterization of CaF2 and rare earth doped CaF2 films

Calcium fluoride (CaF2) and the rare earth doped CaF2 films have been electrodeposited on indium tin oxide (ITO) electrode through electrochemical generation of acid in aqueous solutions near room temperature. For CaF2 film electrodeposition, the local pH at ITO surface is lowered by the electrochemical oxidation of ascorbate anion, and then the Ca-ethylene diamine tetraacetic acid disodium complexes which are close to the ITO electrode are decomposed to release free Ca2+ to react with F- to form CaF2 deposit onto ITO. In the same way, RE-doped CaF2 films have been electrodeposited onto ITO electrode. The morphology of films studied by scanning electron microscopy revealed that they are agglomerated and dense. The films showed a little [111] preferred orientation by X-ray diffraction. It was also proved that doped RE ions were distributed homogeneously in the film by energy dispersive spectroscopy mapping. The optical properties of the electrodeposited CaF2, CaF2:Eu and CaF2:Tb films were studied by photoluminescence, and all films exhibit intense emission peaks. (C) 2011 Elsevier B.V. All rights reserved.