Role of tip structure and surface relaxation in atomic resolution dynamic force microscopy: CaF2(111) as a reference surface

Adam S. Foster, Clemens Barth, Alexander L. Shluger, Risto M. Nieminen, and Michael Reichling
Phys. Rev. B 66, 235417 – Published 27 December 2002
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Abstract

By combining experimental dynamic scanning force microscope (SFM) images of the CaF2(111) surface with an extensive theoretical modeling, we demonstrate that the two different contrast patterns obtained reproducibly on this surface can be clearly explained in terms of the change of the sign of the electrostatic potential at the tip end. We also present direct theoretical simulations of experimental dynamic SFM images of an ionic surface at different tip-surface distances. Experimental results demonstrate a qualitative transformation of the image pattern, which is fully reproduced by the theoretical modeling and is related to the character of tip-induced displacements of the surface atoms. The modeling of the image transformation upon a systematic reduction of the tip-surface distance with ionic tips allows an estimate of the tip-surface distance present in experiment, where 0.28–0.40 nm is found to be optimal for stable imaging with well-defined atomic contrast. We also compare the modeling with ionic tips to results for a pure silicon tip. This comparison demonstrates that a silicon tip can yield only one type of image contrast and that the tip-surface interaction is not strong enough to explain the image contrast observed experimentally. The proposed interpretation of two types of images for the CaF2(111) surface can also be used to determine the chemical identity of imaged features on other surfaces with similar structure.

  • Received 23 July 2002

DOI:https://doi.org/10.1103/PhysRevB.66.235417

©2002 American Physical Society

Authors & Affiliations

Adam S. Foster1, Clemens Barth2, Alexander L. Shluger3, Risto M. Nieminen1, and Michael Reichling4

  • 1Laboratory of Physics, Helsinki University of Technology, P.O. Box 1100, 02015 HUT, Finland
  • 2CRMC2-CNRS, Campus de Luminy Case 913, 13288 Marseille Cedex 09, France
  • 3Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
  • 4Department Chemie, Universität München, Butenandtstraße 5-13 E, 81377 München, Germany

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Vol. 66, Iss. 23 — 15 December 2002

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