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A study of topographic effects on chemical force microscopy using adhesive force mapping
Fuminobu Sato1, Hiroki Okui, Uichi Akiba
1Department of Biomolecular Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan. mfujihir@bio.titech.ac.jp
Ultramicroscopy
|June 13, 2003
Summary
Surface topography, not chemical differences, primarily causes variations in measured adhesive forces. Atomic force microscopy revealed that grain size and contact multiplicity on gold surfaces significantly broaden adhesive force histograms.
Area of Science:
- Surface science
- Nanotechnology
- Materials science
Background:
- Adhesive forces are crucial in surface interactions.
- Understanding adhesive force variations is key for nanotechnology applications.
- Atomic force microscopy (AFM) is a primary tool for measuring surface forces.
Purpose of the Study:
- Investigate the origins of peak broadening in adhesive force histograms.
- Determine the influence of surface topography versus chemical termination on adhesive forces.
- Analyze adhesive force distributions on gold surfaces with varying topographies.
Main Methods:
- Utilized pulsed-force-mode atomic force microscopy (PFM-AFM) to measure adhesive forces in water.
- Prepared gold surfaces using microcontact printing and self-assembly methods.
- Employed CH(3)- and COOH-terminated surfaces and CH(3)-terminated AFM tips.
Main Results:
- Surface topography, specifically grain size and multiplicity of tip-grain contacts, was identified as the main cause of peak broadening.
- Homogeneously chemically modified surfaces showed less broadening compared to topographically varied surfaces.
- Microcontact printing on fine-grained gold resulted in distinct chemical regions, but topography still dominated force distribution.
Conclusions:
- Topographic effects significantly influence and broaden the distribution of measured adhesive forces.
- Minimizing topographic variations is essential for obtaining narrow adhesive force distributions.
- AFM measurements are sensitive to nanoscale surface features, impacting observed force profiles.