STM atomic-scale characterization of the γ′-Al2O3 film on Ni3Al(111)

We report the first atomic-resolution study by scanning tunneling microscopy (STM) of the gamma'-Al2O3 film formed on the Ni3Al(111) surface at similar to 1000-1100 K. STM images of this well-ordered oxide film reveal a hexagonal array of corrugations with an average interatomic spacing of 3.0+/-0.1 Angstrom. The low-energy electron diffraction (LEED) pattern of the aluminum oxide film reveals the ordering of O2- ions in the surface. On the basis of LEED data and theoretical considerations, the corrugations in the STM atomic-resolution images are tentatively assigned to oxygen anions. Annealing the oxide prepared at similar to 300 K to similar to 1100 K results in the appearance of a metallic aluminum peak in the Auger electron spectra and a substantial increase in the Al-(1396)/Ni-(848) ratio, indicating aluminum segregation close to the surface. (C) 1999 Elsevier Science B.V. All rights reserved.