Friction and Load on Well Defined Surfaces Studied by Atomic Force Microscopy
Atomic Friction Force Microscopy AFM FFM Friction is measured on surfaces including mica, gold films with self assembled monolayers and cleaved crystals in UHV. Factors that affect quantitative measurements such as tip radius, scan direction and environmental conditions are evaluated.
The atomic force microscope is an important new tool for investigating the mechanisms of friction on the atomic and molecular scale. AFM studies have now provided atomic lattice resolution images on a wide range of surfaces — metals in air and electrolytes, cleaved ionic crystals, molecular films on surfaces, and layered compounds like graphite and mica. We are now in a position to address some important questions based on a good range of data. One major question is the mechanism of AFM imaging with lattice resolution at high loads, where a single atom contact is not possible given the strength of materials. The “dragging flake” mechanism suggested for layered systems is not general enough to explain the wide range of results available today. Other questions involve friction measurements. What is the relation of AFM lateral force measurements to macroscopic friction? How general is “stick slip” motion? We do not answer these questions here, but we hope to advance the discussion.
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