Iridium L_3-edge and oxygen K-edge x-ray absorption spectroscopy of nanocrystalline iridium oxide thin films

摘要

Structural investigations of the short range order around iridium and oxygen ions in nanocrystalline iridium oxide thin films, prepared by dc magnetron sputtering technique, were performed by x-ray absorption spectroscopy. The Ir L_3-edge extended x-ray absorption fine structure (EXAFS) and the O K-edge x-ray absorption near edge structure (XANES) signals were measured at room temperature and analysed within ab initio multiple-scattering and full-multiple-scattering approaches, respectively. The x-ray absorption spectroscopy results indicate the presence in the films of ordered regions - nanocrystals, having a size of about 10 A and a structure rather close to that in crystalline iridium oxide IrO_2. Such evidence agrees well with observations by x-ray diffraction, suggesting that the thin films are x-ray amorphous.