The influence of surface preparation on the structures of nickel oxide formed on the (100) face of nickel

A study has been made on the influence of surface preparation involving abrasion, electropolishing, and vacuum annealing on the physical nature of the (100) nickel crystal face and on the morphological development of the oxide film. The structure of the initial surface was dependent upon the method of surface preparation, but electropolished specimens subjected to conventional or high vacuum anneals at 10−6 and 10−10 Torr, respectively, and temperatures of 800 and 700° C were structurally identical. Thermal faceting of surfaces prepared to correspond to the (100) plane was negligible. Oxidation at 500° C and over the oxygen pressure range 10−5−400 Torr led to formation of polycrystalline oxide crystallites randomly distributed over the surface during early stage exposures; the crystallites were only a few hundred Angstroms in size upon coverage of the surface by a nickel oxide film. These films were relatively uniform for thicknesses up to 2000 Å. Crystallite growth processes led to three major epitaxial relationships between oxide and metal: (100)NiO, (111)NiO, and (211)NiO ∥ (100)Ni.