On the electrodeposition of tantalum from three different ionic liquids with the bis(trifluoromethyl sulfonyl) amide anion

The electrodeposition of Ta from TaF5 was studied in three different ionic liquids, namely in 1-butyl-1-methylpyrrolidinium bis(trifluoromethyl sulfonyl) amide, 1-ethyl-3-methylimidazolium bis(trifluoromethyl sulfonyl) amide and 1-methyl-3-propyl imidazolium bis(trifluoromethyl sulfonyl) amide. The electrochemical quartz crystal microbalance (EQCM) was used together with electrochemical techniques for characterizing in situ the electrodeposition process. With the help of the EQCM we could identify the stoichiometry of the electrodeposited species. Furthermore, square-wave voltammery was used to study intermediate reduction processes in the potential regime where no mass change was detected. An XPS analysis proved the existence of elemental Ta, besides some oxides and Ta halide species. Both the ionic liquid and the deposition conditions influence strongly the quality and properties of the deposited layers.