title: Noncontact atomic force microscopy study of the spinel MgAl(2)O(4)(111) surface.
abstract: Based on high-resolution noncontact atomic force microscopy (NC-AFM) experiments we reveal a detailed structural model of the polar (111) surface of the insulating ternary metal oxide, MgAl(2)O(4) (spinel). NC-AFM images reveal a 6√3×6√3R30° superstructure on the surface consisting of patches with the original oxygen-terminated MgAl(2)O(4)(111) surface interrupted by oxygen-deficient areas. These observations are in accordance with previous theoretical studies, which predict that the polarity of the surface can be compensated by removal of a certain fraction of oxygen atoms. However, instead of isolated O vacancies, it is observed that O is removed in a distinct pattern of line vacancies reflected by the underlying lattice structure. Consequently, by the creation of triangular patches in a 6√3×6√3R30° superstructure, the polar-stabilization requirements are met.
authors.affiliation: Interdisciplinary Nanoscience Center and Department of Physics and Astronomy, Aarhus University, Ny Munkegade, DK-8000 Aarhus C, Denmark.
authors.forename: Morten K
authors.initials: MK
authors.lastname: Rasmussen
authors.forename: Kristoffer
authors.initials: K
authors.lastname: Meinander
authors.forename: Flemming
authors.initials: F
authors.lastname: Besenbacher
authors.forename: Jeppe V
authors.initials: JV
authors.lastname: Lauritsen