Atomic-scale friction on diamond(111) studied by ultra-high vacuum atomic force microscopy

Abstract

The frictional properties of a diamond(111) single-crystal surface have been studied using an ultra-high vacuum atomic force microscope, while the presence or absence of hydrogen on the surface was monitored by low-energy electron diffraction (LEED). We have observed, for the first time, atomic-scale stick-slip features of a silicon tip on the hydrogen-terminated (1 × 1) diamond(111) surface. The distance between the stick-slip rows, measured perpendicularly to the rows, is typically 2–3 Å, consistent with the lattice parameters of diamond. Removal of the hydrogen from the surface, indicated by a change in LEED pattern from (1 × 1) to (2 × 1), gives rise to enormous stick-slip features at larger scale. The average friction coefficient on the hydrogen-free surface is found to be more than two orders of magnitude larger than on the hydrogen-terminated surface for loads up to 30 nN.