Stick–slip motion in the atomic force microscope |
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Authors: | KL Johnson J Woodhouse |
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Affiliation: | (1) Cambridge University Engineering Department, Trumpington Street, Cambridge, CB2 1PZ, UK |
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Abstract: | Measurements of atomic friction in the atomic force microscope frequently show periodic variations at the lattice spacing
of the surface being scanned, which have the saw‐tooth wave form characteristic of “stick–slip” motion. Simple models of this
behaviour have been proposed, in which the “dynamic element” of the system is provided by the elastic stiffness and inertia
of the cantilever which supports the tip of the microscope, in its lateral, i.e., torsional mode of vibration. These models
have been successful in predicting the observed motion, but only by assuming that the cantilever is heavily damped. However,
the source of this damping in a highly elastic cantilever is not explained. To resolve the paradox, it is shown in this note
that it is necessary to introduce the elastic stiffness of the contact into the model. The relationship between the contact
stiffness, the cantilever stiffness and the amplitude of the periodic friction force is derived in order for stick–slip motion
at lattice spacing to be achieved.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | nano‐ tribology atomic friction atomic force microscopy |
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