Noncontact Atomic Force Microscopy - Yale School of Engineering ...

P.II-25
Contrast formation on cross-linked (1x2) reconstructed titania (110)
Hans H. Pieper 1 , Stefan Torbrügge 1,2 , Stephan Bahr 1,2 , Krithika Venkataramani 1,3 ,
Angelika Kühnle 1 and Michael Reichling 1
1 Fachbereich Physik, Universität Osnabrück, Barbarastraße 7, 49076 Osnabrück, Germany
2 present address: SPECS GmbH, Voltastrasse 5, 13355 Berlin, Germnay
3 present address: iNano, Aarhus University, DK-8000 Aarhus C, Denmark
In NC-AFM imaging, the tip structure plays a prominent role in atomic contrast
formation. It is, for instance, possible to image the cationic or the anionic sub-lattice of
CaF2(111) by changing the tip termination [1]. For the unreconstructed rutile TiO2 (110)
at least a third mode is known [2].
Here, we investigate the cross-linked (1x2) surface reconstruction of rutile
TiO2(110), which has been studied both with STM and NC-AFM, however, the atomic
structure is still discussed controversially. We present NC-AFM results, which will be
interpreted with respect to tip termination and tip-surface distance. A comparison with
existing models provides strong evidence for one of these models.
Figure 1: Three consecutive images of the cross-linked (1x2) titania surface taken with different
tip terminations. The left image is taken with a positive tip termination. A contact with the sample
leads to a negative tip termination (middle image). The tip in the right picture is unidentified.
Figure 2: High resolution measurements are in good agreement with the surface model suggested
by Bennett [3] as shown to the right.
[1] C. Barth et al. J. Phys.: Condens. Matter 13, 2061 (2001)
[2] G.H. Enevoldsen et al. Phys. Rev. B 76, 205415 (2007)
[3] R.A. Bennett et al. Phys. Rev. Lett. 82, 3831 (1999)
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