ATOMIC-SCALE FRICTION ON DIAMOND(111) STUDIED BY ULTRA-HIGH-VACUUM ATOMIC-FORCE MICROSCOPY

The frictional properties of a diamond(111) single-crystal surface hav e been studied using an ultra-high vacuum atomic force microscope. whi le the presence or absence of hydrogen on the surface was monitored by low-energy electron diffraction (LEED). We have observed, for the fir st time, atomic-scale stick-slip features of a silicon tip on the hydr ogen-terminated (1 x 1) diamond(111) surface. The distance between the stick-slip rows. measured perpendicularly to the rows, is typically 2 -3 Angstrom, consistent with the lattice parameters of diamond. Remova l of the hydrogen from the surface, indicated by a change in LEED patt ern item (1 x 1) to (2 x 1), gives rise ro enormous stick-slip feature s at larger scale. The average friction coefficient on the hydrogen-fr ee surface is found to be more than two orders of magnitude larger tha n on the hydrogen-terminated surface for loads rip to 30 nN. (C) 1997 Elsevier Science B.V.