An ESCA study of the interaction of oxygen with the surface of ruthenium

The interaction of oxygen with the surface of a Ru wafer in the range of room temperature to 600°C was investigated by ESCA. Ru3d,3p,MVV, valence band and 01s spectra were recorded. Three different states of oxygen were observed on the Ru wafer surface. Definitive identification of two of the three states was achieved according to the multiplet structure in the photoemission spectra of oxygen and the binding energy of various states of oxygen. The oxygen species identified are O2- and dissolved atomic oxygen. The third oxygen state which gives rise to the peak at a BE of 532.3 eV in the O1s spectrum and 11.7 eV in the photoemission spectrum is tentatively assigned to a chemisorbed hydroperoxy radical. A discussion of the Ru oxidation process is also given.