Frictional Properties of Organosilane Self-Assembled Monolayer in Vacuum

概要

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Frictional properties of methyl (CH3)- and fluoromethyl (CF3)-terminated organosilane self-assembled monolayers (SAMs) have been studied by lateral force microscopy (LFM). The SAMs were prepared on Si substrates by means of chemical vapor deposition using n-octadecyltrimethoxysilane or heptadecafluoro-1,1,2,2-tetrahydro-1-trimethoxysilane as a precursor. In spite of the fact that the CF3-terminated SAM was more hydrophobic than the CH3-terminated SAM, the CF3-terminated SAM was adsorbed a larger amount of water than the CH3-terminated SAM because of the strong electron negativity of F atoms. Consequently, the capillary force effect in LFM appeared more distinctly on the CF3-terminated SAM@. The difference in capillary force between the CH3- and CF3-terminated SAMs was responsible for greater friction forces in air on the CF3-terminated SAM, in addition to the intrinsic difference in frictional properties between the CH3 and CF3 groups. With increasing temperature, CH3- and CF3-terminated SAMs became more lubricant due to more increasing molecular vibration. Furthermore, both SAMs were so robust that no damage was induced by probe scanning in vacuum even at a temperature of 300°C and an applied load force of 600 nN.
Publication Office, Japanese Journal of Applied Physics, Faculty of Science, University of Tokyoの論文
2001-06-30