Structure of the Ultrathin Aluminum Oxide Film on NiAl(110)

Abstract

The well-ordered aluminum oxide film formed by oxidation of the NiAl(110) surface is the most intensely studied metal surface oxide, but its structure was previously unknown. We determined the structure by extensive ab initio modeling and scanning tunneling microscopy experiments. Because the topmost aluminum atoms are pyramidally and tetrahedrally coordinated, the surface is different from all Al 2 O 3 bulk phases. The film is a wide-gap insulator, although the overall stoichiometry of the film is not Al 2 O 3 but Al 10 O 13 . We propose that the same building blocks can be found on the surfaces of bulk oxides, such as the reduced corundum (0001) surface.