Sputter-Induced Modifications of IrO2 During XPS Measurements

We have characterized sputter-induced modifications of IrO2 during low-energy Ar+ bombardment. The O 1s peak contains at least two components whose intensity drops by a factor of 2 after 10 min of sputtering at 2.5 kV. The relative peak areas of the Ir 4d5/2–7/2 features are altered and their binding energies shift downward by −0.4 eV after sputtering. The unusual Ir 4d5/2–7/2 ratio before sputtering may indicate higher oxidation states and/or poor preparation from the metal chloride; however, the Ir 4f7/2 BE of 61.5 eV is consistent with a principal IrO2 composition. The drop in O 1s intensity and lower binding energy indicate that reduction to Ir metal occurs durng Ar+ irradiation.