Line defects of a thin alumina film on NiAl(110) were studied on the atomic level with scanning tunneling microscopy at 4K. While boundaries between two reflection domains did not expose a characteristic structure, antiphase domain boundaries were well ordered. The latter boundaries result from the insertion of a row of O atoms, as atomically resolved images of the topmost O layer show. The insertion occurred only in 2 of the 2 characteristic directions of the quasi-hexagonal O lattice. Depending on the direction, either straight or zig-zagged boundaries form. An atomic characterization of line defects on the oxide surface was a first step to correlate their topographic structure and chemical activity.

Atomic Structure of Antiphase Domain Boundaries of a Thin Al2O3 Film on NiAl(110). M.Kulawik, N.Nilius, H.P.Rust, H.J.Freund: Physical Review Letters, 2003, 91[25], 256101 (3pp)