ABSTRACT
Friction at the nanoscale has become a signicant challenge for microsystems, including MEMS, NEMS and other devices. At nanoscale, lateral loading often causes component breakage and loss of functions in devices; therefore, accurate measurement and understanding of nanofriction are critical in device reliability and durability. Since silicon-based devices offer overwhelming cost advantages in manufacturing, the issue of controlling friction on silicon using nanometer thin lms has attracted signicant interest recently, in addition to lubrication by a thin layer of water in rare cases. Due to the small scale of measurements, the atomic force microscope (AFM) has been the instrument of choice to measure nanofriction. At the same time, a detailed surface characterization of the monolayer lm structure is needed. This chapter explores the use of near-edge x-ray absorption ne structure (NEXAFS) spectroscopy and Fourier transform infrared (FTIR) spectroscopy to ascertain the order of the lm. A series of n-alkyltrichlorosilanes self-assembled monolayer lms with various chain lengths (C5 to C30) were prepared on silicon (100) surfaces. Nanofriction measurements were conducted using an atomic force microscope (AFM). Results showed that the lowest friction was obtained with a C12 lm with higher friction values observed for C5 and C30 lms. The lm structure and order of organization were probed with an x-ray absorption technique (NEXAFS) in conjunction with Fourier transform infrared (FTIR) spectroscopy. It was observed that C12, C16, and C18 lms were more ordered (molecular orientation of the carbon backbone nearly perpendicular to the surface) than those of C5 and C30 lms. The combination of these two techniques provides complementary evidence that both lm order and organization strongly inuence nanofriction.
