The electronic properties of 1-dimensional defects in ultra-thin Al2O3 films were investigated by low-temperature STM and STS. Whereas line defects between two oxide domains exhibited almost no topographic contrast in low bias images, they appeared with a distinct corrugation at higher positive sample bias. Conductance spectroscopy and imaging revealed 3 unoccupied states at +2.5, +3.0 and +4.5 V localized along the domain boundaries. The defect-induced states were responsible for the observed contrast variation and originate most likely from a non-stoichiometric oxide composition at the interface between two Al2O3 domains.

Defect-Induced Gap States in Al2O3 Thin Films on NiAl(110). N.Nilius, M.Kulawik, H.P.Rust, H.J.Freund: Physical Review B, 2004, 69[12], 121401 (4pp)