Direct measurement of forces during scanning tunneling microscope imaging of graphite

The normal force acting on a scanning tunneling microscope tip while imaging a graphite surface in air has been measured directly. Forces in the range of 10 −7 to 10 −6 N are required to achieve tunneling. Further, the force needed to maintain a constant current varies considerably as the tip scans...

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Bibliographic Details
Published in:Surface science 1989-02, Vol.208 (3), p.473-486
Main Authors: Mate, C.Mathew, Erlandsson, Ragnar, McClelland, Gary M., Chiang, Shirley
Format: Article
Language:English
Subjects:
Exact sciences and technology
Instruments, apparatus, components and techniques common to several branches of physics and astronomy
Other topics in instruments, apparatus, components and techniques common to several branches of physics and astronomy
Physics
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Summary:The normal force acting on a scanning tunneling microscope tip while imaging a graphite surface in air has been measured directly. Forces in the range of 10 −7 to 10 −6 N are required to achieve tunneling. Further, the force needed to maintain a constant current varies considerably as the tip scans from one part of the graphite unit cell to another. Our results are consistent with a model, originally suggested by Mamin et al., in which the force between the tip and the surface is mediated by a contamination layer, and tunneling occurs at the end of an asperity which pierces this layer. However, we cannot rule out a model where a graphite flake is dragged across the graphite surface to generate an STM image.
ISSN:0039-6028
1879-2758
DOI:10.1016/0039-6028(89)90014-9