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

Site-specific force spectroscopy on TiO2 (110) surface at lowtemperature
A. Yurtsever, A. Pratama, Y. Sugimoto, M. Abe, and S. Morita
Graduate School of Engineering, Osaka University, Osaka, Japan
We-0920
Non-contact AFM (nc-AFM) has opened the way for the measurement of the forces
that are generated between different kinds of interaction on surfaces. Using the homemade
low temperature nc-AFM, we study the site-specific force spectroscopy on the
rutile TiO2 (110)-(1x1) metal oxide surface. The rutile TiO2(110) surface has been
intensively used as a subject of numerous surface science investigations over the years
due to its wide variety of technological applications such as catalysis, solar cells, surface
protective coatings, and gas sensing devices for pollution control [1]. In AFM, imaging of
metal-oxide surfaces, the image contrast strongly depends on the chemical constitution of
the surface layer and the chemical identity of the tip-apex structure [2]. Depending on the
polarity of tip-apex charged state, the distinct types of image contrast are observed. In
order to clarify the imaging mechanism of each contrast modes, we need to perform the
measurement of force-displacement curves on this surface. By employing the atomtracking
technique [3], force–distance measurements over three different atomic sites,
using three different tip states, were obtained. We observe that the maximum attractive
interaction force is smallest on OH groups for different tip-apex states. In this
contribution, we will discuss the effect of the different tip terminations on interaction
force over surface atomic (e.g., Ob, Ti) and defect (e.g., OH) sites.
Figure 1: Low-temperature atomic force microscopy spectroscopic measurements over various
sites in the TiO2 (110) surface. The force versus distance data obtained with a neutral tip (e.g., Si)
(a) and with a positively terminated tip (b). Inset: Shows the corresponding topographic images of
each contrast modes at the same surface area.
[1] U. Diebold, Surf. Sci. Rep. 48, 53-229 (2003).
[2] G. H. Enevoldsen et al., Phys. Rev. B 78, 045416 (2008).
[3] M. Abe et al., Appl. Phys. Lett. 90, 203103 (2007).
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