Electrodeposition and characterization of CaF_2 and rare earth doped CaF_2 films

摘要

Calcium fluoride (CaF_2) and the rare earth doped CaF_2 films have been electrodeposited on indium tin oxide (ITO) electrode through electrochemical generation of acid in aqueous solutions near room temperature. For CaF_2 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 Ca~2+ to react with F~-to form CaF_2 deposit onto ITO. In the same way, RE-doped CaF_2 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 CaF_2, CaF_2:Eu and CaF_2:Tb films were studied by photoluminescence, and all films exhibit intense emission peaks.