Atomic-Scale Friction and Microfriction of Graphite and Diamond Using Friction Force Microscopy.

摘要

Friction of graphite and diamond surfaces against a sharp silicon nitride tip was measured using a friction force microscope (FFM). Atomic-scale friction of a freshly cleaved highly oriented pyrolytic graphite (HOPG) exhibited the same periodicity as that of corresponding topography. However, the peaks in friction and those in corresponding topography profiles were displaced relative to each other. Using Fourier expansion of the interaction potential, we have calculated interatomic forces between the FFM tip and graphite surface. We have shown that the variations in atomic-scale friction and the observed displacement between the peaks in friction and those in corresponding topography can be explained by the variations in interatomic forces in the normal and lateral directions. At large scan sizes (50 nm x 50 nm or larger), the variation of friction for graphite and a single-crystal (IIa) diamond was found to follow the local slope of the sample surface, suggesting that a ratchet mechanism is operative in microscale friction.