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Velocity dependent friction laws in contact mode atomic force microscopy
Robert W Stark1, Georg Schitter, Andreas Stemmer
1Nanotechnology Group, Swiss Federal Institute of Technology Zurich, ETH Zentrum/CLA, CH-8092 Zurich, Switzerland. stark@nanomanipulation.de
Ultramicroscopy
|July 3, 2004
Summary
Friction in atomic force microscopy (AFM) dynamics is explored using a multi-asperity contact model. Simulations reveal two regimes: steady sliding and stick-slip, influenced by scan velocity and friction properties.
Area of Science:
- Surface science
- Tribology
- Nanotechnology
Background:
- Friction forces at the tip-sample interface are critical for contact mode atomic force microscopy (AFM) dynamics.
- Ambient conditions involve contact radii of a few nanometers, necessitating models that account for larger interaction areas.
Purpose of the Study:
- To investigate the dynamics of contact mode AFM under a multi-asperity contact interface assumption.
- To model kinetic friction force as a product of real contact area and interfacial shear strength.
- To analyze the velocity strengthening of lateral force using a logarithmic shear-strength-velocity relationship.
Main Methods:
- Development of an empirical model for multi-asperity contact in AFM.
- Numerical simulations to explore system dynamics under varying conditions.
- Investigation of the influence of scan velocity and interfacial friction on system behavior.
Main Results:
- Identification of two distinct dynamic regimes in contact mode AFM: steady sliding and stick-slip.
- Demonstration that system state depends on scan velocity and the velocity dependence of interfacial friction.
- Observation that even minor viscous damping can suppress stick-slip oscillations.
Conclusions:
- The multi-asperity contact model provides insights into AFM dynamics.
- Understanding friction regimes is crucial for controlling AFM operation.
- Viscous damping is an effective mechanism for stabilizing AFM tip-sample interactions.