Interpretation of the x-ray photoemission spectra of cobalt oxides and cobalt oxide surfaces

CoO and Co3O4 have been studied by high-resolution X-ray photoemission. The characteristic binding energies in the Co 2p32, 2p12, and 3s regions, their band shapes and widths, the associated shake-up structure, the O(1s) and O(2s) BE's, and the valence band spectra have been examined. The two oxides are readily distinguished from their spectra though it is shown that the O(1s) BE's are identical at 529.50 ± 0.14 eV. Argon and oxygen ion sputtered surfaces were examined to establish the integrity of the oxides. A higher BE O(1s) component (530.7–531.6 eV), the intensity and BE of which vary with the treatments mentioned above, corresponds to non-stoichiometric surface oxygen. The results are discussed with respect to the electronic structures of the oxides and the often conflicting earlier studies of these oxides.