title: Defects in oxide surfaces studied by atomic force and scanning tunneling microscopy.
abstract: Surfaces of thin oxide ﬁlms were investigated by means of a dual mode NC-AFM/STM. Apart from imaging the surface termination by NC-AFM with atomic resolution, point defects in magnesium oxide on Ag(001) and line defects in aluminum oxide on NiAl(110), respectively, were thoroughly studied. The contact potential was determined by Kelvin probe force microscopy (KPFM) and the electronic structure by scanning tunneling spectroscopy (STS). On magnesium oxide, different color centers, i.e., F(0), F(+), F(2+) and divacancies, have different effects on the contact potential. These differences enabled classiﬁcation and unambiguous differentiation by KPFM. True atomic resolution shows the topography at line defects in aluminum oxide. At these domain boundaries, STS and KPFM verify F(2+)-like centers, which have been predicted by density functional theory calculations. Thus, by determining the contact potential and the electronic structure with a spatial resolution in the nanometer range, NC-AFM and STM can be successfully applied on thin oxide ﬁlms beyond imaging the topography of the surface atoms.
authors: Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany.
authors: Thomas
authors: T
authors: König
authors: Georg H
authors: GH
authors: Simon
authors: Lars
authors: L
authors: Heinke
authors: Leonid
authors: L
authors: Lichtenstein
authors: Markus
authors: M
authors: Heyde