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

The interaction of oxygen with the (001) surface of a metastable cubic coba lt 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 mo dulated electron emission, X-ray photoelectron spectroscopy and Auger elect ron 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 th e square unit cell of the unreacted, underlying cobalt film. A relevant fra ction of cobalt and oxygen atoms with reduced coordination has been detecte d 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 fil m. For both room-temperature and high-temperature growth conditions, the re sulting oxide layer is tetragonally distorted. (C) 1999 Elsevier Science B. V. All rights reserved.