Growth and structure of cobalt oxide on (001) bct cobalt film

The interaction of oxygen with the (001) surface of a metastable cubic cobalt film, 10 monolayers (ML) thick, epitaxially grown on the Fe(001) surface, has been studied at 300 and 470 K by means of primary-beam diffraction modulated electron emission, X-ray photoelectron spectroscopy and Auger electron spectroscopy. At 300 K the formation of 7 ML of CoO has been observed, in the typical rocksalt structure, rotated by 45 degrees with respect to the square unit cell of the unreacted, underlying cobalt film. A relevant fraction of cobalt and oxygen atoms with reduced coordination has been detected which does not affect significantly the local order in the oxide film. At 470 K, the oxide extends in thickness involving almost the full cobalt film. For both room-temperature and high-temperature growth conditions, the resulting oxide layer is tetragonally distorted. (C) 1999 Elsevier Science B.V. All rights reserved.