Atomic structure of a stripe phase on Al2O3/Ni3Al(111) revealed by scanning force microscopy

The most remarkable feature of the ultrathin aluminum oxide film grown on Ni3Al(111) as reported in the literature is its surface reconstruction resulting in a dot structure with a large rhombic surface unit cell. Here, we demonstrate that this is the reconstruction of the dominant phase of the oxide film, while 5%-20% of the surface area may be covered by another reconstruction that is characterized by zigzag features arranged in parallel stripes. When investigated with scanning tunneling microscopy, this stripe phase appears to be very different from the dominant phase; however, highest resolution dynamic scanning force microscopy operated in the noncontact mode reveals great similarity of the atomic structures. Both phases consist of a modulated hexagonal lattice with 0.51 nm periodicity resembling the aluminum sublattice of the Ni3Al(111) substrate.