Interaction of Oxygen with (110) Nickel

The interaction of oxygen with a (110) nickel surface has been studied by photoelectric and low-energy electron diffraction techniques. With increasing exposure to O2, a sequence of oxygen—nickel structures is formed terminating in the NiO rocksalt structure which is oriented with the (100) face of the oxide parallel to the surface. It was possible to observe some of these structures in reverse order by heating the oxide-covered crystal in vacuum or subjecting it to brief argon ion bombardment. From the fact that the oxide was decomposed at only 200°C, and from the associated changes in work function and diffraction intensity, it is concluded that oxygen readily penetrates into the nickel lattice, occupying substitutional sites to form three-dimensional oxygen—nickel structures of increasing oxygen content until the composition of NiO is reached. This makes possible the correlation of the two-dimensional oxygen—nickel structures observed on different faces.