CoO 111/ surface study by surface X-ray diffraction

We present a structural investigation of the polar 111. surface of CoO single crystals by grazing incidence X-ray diffraction. The surface is found to be always covered by a ;50 A° -thick spinel Co3O4 layer that was quantitatively characterized. Attempts to remove this layer by UHV annealings or Arq bombardments lead to the formation of metallic Co clusters on the surface that transform again in Co3O4 by annealing under oxygen. q2000 Elsevier Science B.V. All rights reserved.