title: Chemical identification of point defects and adsorbates on a metal oxide surface by atomic force microscopy.
abstract: Atomic force microscopy in the non-contact mode (nc-AFM) can provide atom-resolved images of the surface of, in principle, any material independent of its conductivity. Due to the complex mechanisms involved in the contrast formation in nc-AFM imaging, it is, however, far from trivial to identify individual surface atoms or adsorbates from AFM images. In this work, we successfully demonstrate how to extract detailed information about defects and the chemical identity of adsorbates on a metal oxide surface from nc-AFM images. We make use of the observation that the apex of the AFM tip can be altered to expose either a positive or negative tip termination. The complementary set of images recorded with the two tip terminations unambiguously define the ionic sub-lattices and reveal the exact positions of oxygen vacancies and hydroxyl (OH) defects on a TiO(2) surface. Chemical specificity is extracted by comparing the characteristic contrast patterns of the defects with results from comprehensive AFM simulations. Our methodology of analysis is generally applicable and may be pivotal for uncovering surface defects and adsorbates on other transition metal oxides designed for heterogeneous catalysis, photo-electrolysis or biocompatibility.
authors: Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark.
authors: Jeppe V
authors: JV
authors: Lauritsen
authors: Adam S
authors: AS
authors: Foster
authors: Georg H
authors: GH
authors: Olesen
authors: Mona C
authors: MC
authors: Christensen
authors: Angelika
authors: A
authors: Kühnle
authors: Stig
authors: S
authors: Helveg
authors: Jens R
authors: JR
authors: Rostrup-Nielsen
authors: Bjerne S
authors: BS
authors: Clausen
authors: Michael
authors: M
authors: Reichling
authors: Flemming
authors: F
authors: Besenbacher