Friction and wear properties of smooth diamond films grown in fullerene-argon plasmas

摘要

In this study, we describe the growth mechanism and the ultralow friction and wear properties of smooth (20-50 nm rms) diamond films grown in a microwave plasma consisting of Ar and fullerene (the carbon source). The sliding friction coefficients of these films against Si(sub 3)N(sub 4) balls are 0.04 and 0.1 in dry N(sub 2) and air, which are comparable to that of natural diamond sliding against the same pin material, but is lower by factors of 5 to 10 than that afforded by rough diamond films grown in conventional H(sub 2)-CH(sub 4) plasmas. Furthermore, the smooth diamond films produced in this work afforded wear rates to Si(sub 3)N(sub 4) balls that were two to three orders of magnitude lower than those of H(sub 2)-CH(sub 4) grown films. Mechanistically, the ultralow friction and wear properties of the fullerene-derived diamond films correlate well with their initially smooth surface finish and their ability to polish even further during sliding. The wear tracks reach an ultrasmooth (3-6 nm rms) surface finish that results in very little abrasion and ploughing. The nanocrystalline microstructure and exceptionally pure sp(sup 3) bonding in these smooth diamond films were verified by numerous surface and structure analytical methods, including x-ray diffraction, high-resolution AF-S, EELS, NEXAFS, SEM, and TEM. An AFM instrument was used to characterize the topography of the films and rubbing surfaces.