Near Frictionless Behavior of Hydrogen Plasma Treated Diamond Nanowire Films

[[abstract]]The diamond nanowires (DNW) films have been deposited by N2-based microwave plasma enhanced chemical vapor deposition. Hydrogen plasma treatment is carried out on these films for various treatment times which result in microstructural and chemical modification. Morphology of as-grown DNW films resemble symmetry of dense grains composed in nanowires; however the wires break into ultrasmall, randomly distributed spherical shaped grains after 15 minutes of H2 plasma treatment. Transmission electron microscopy depicts that as-grown DNW films mainly consist of diamond nanocrystals with graphitic sp2C—C bonded grain boundaries. However, the graphitic grain boundaries do not exist after H2 plasma treatment on DNW films. Raman spectroscopy and near edge X-ray absorption fine structure spectroscopy studies reveal that after H2 plasma treatment the films possess large fraction of sp3 C—C and C—H bonding in the form of trans-polyacetylene symmetry of sp2 CH x . Interestingly, the friction coefficient of 0.0001 is obtained for the 15 minutes H2 plasma treated DNW films. Such an extent of low valued friction coefficient is described by the passivation of uncompensated carbon dangling bonds by hydrogen content and adsorption of H2 O molecules. Furthermore, in low humid atmosphere, the friction coefficient is found to be consistently increased which confirms the insufficient chemical passivation of carbon dangling bonds.[[booktype]]紙