X- ray photoemission study of the interaction of oxygen and air with clean cobalt surfaces

Abstract

The interaction of oxygen with polycrystalline cobalt surfaces has been studied at 300 K (1 × 10-6 to 1 × 10-5 Torr) using high-resolution (monochromatized) X-ray photoemission. At high exposures (> 100 L nominal) CoO is identified as the product from the nature of the Co 2p 3 2, 2p 1 2, 3s, and valence band spectra. There is no evidence for measurable amounts of Co3O4 or Co2O3. Two O 1s features are observed at both high and low (10L) exposures. The dominant O 1s feature at 529.5 ± 0.2 eV corresponds to the oxide and a minor feature at 531.3 ± 0.2 eV is attributed to non-stoichiometric surface oxygen. Exposure to air produces quite different results, with a dominant O 1s feature at 531.5 ± 0.2 eV and dominant Co 2p 3 2 and 2p 1 2 features centered at 781.3 ± 0.2 eV and 797.1 ± 0.2 eV. These three values are very close to those reported here for bulk Co(OH)2. Ion etching of the air-exposed surface removes this dominant surface product rapidly revealing some oxide and finally metal. © 1976.