Tribology design of micromachine surfaces using the modofication of Fullerene C_<60>

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The objective of this study was to develop ultrasmooth Fullerene C_<60> films for solving microtribological problems of micromachines. For this purpose, molecular beam epitaxy (MBE) has been used to modify molybdenum disulfide (MoS_2) and highly oriented pyrographite (HOPG) surfaces with C_<60> sublimated from the Knudsen cell. The growth and structure of MBE grown C_<60> have been analyzed in-situ with the reflection high energy electron diffraction (RHEED), and it was found that the C_<60> films show close-packed epitaxial growth with its lattice constant of 1.0nm. Thick film with more than 10 monolayrs also showed smooth surface having fcc structure. Atomic force microscopy (AFM) signified that thick C_<60> films have three-fold symmetry domain structure, which coincides with the results obtained by RHEED.The three-fold domain structure of C_<60> has only been made clear by the research group in Basel University, Switzerland and by this study.Microtribolgical properties of MBE grown C_<60> films have been conducted in an ordinary atmosphere using AFM and friction force microscopy (FFM). Ultralow friction was found for C_<60> films. Thick films with more than 10 monolayrs also showed low friction. Friction coefficients of 0.019 and 0.012 were found for MoS_2 and HOPG substrates, respectively. These values are much lower than those reported by the other three research groups, and this may be caused by the uniform and smooth film structure prepared by MBE.Hydrophobic property against water molecules contained in air was found for MBE grown C_<60> films. This strongly suggests microtribological applications of MBE grown C_<60> films to micromachine.