XPS, AES, and Electrochemical Study of Iridium Oxide Coating Materials for Cardiovascular Stent Application

Abstract

The surface composition and morphology of iridium oxide (IrO2) coatings prepared by a multi-step physical vapor deposition process on 316L stainless steel stent substrates has been investigated by XPS, AES, and FESEM. The obtained data show that even though the morphologies of iridium oxide films produced within the examined range of PVD process parameters are almost identical, there is a difference in their surface composition, in particular in the ratios of Ir-O σ and Ir=O π bonds. A correlation between the surface stoichiometries of the IrO2 films and their electrochemical CV and EIS responses has been established. The observed differences in the O 1s photoemission line shape of the investigated iridium oxide films were strikingly reflected in their voltammetric curve features. The implication of these finding on the mechanism of the catalytic decomposition of hydrogen peroxide by IrO2 is discussed.