A. V. Sumant, D. S. Grierson, R. W. Carpick, University of Wisconsin, Madison, Madison, WI; J. E. Gerbi, J. Birrell, J. A. Carlisle, O. Auciello, Argonne National Laboratory, Argonne, IL
The need for materials that exhibit low friction, adhesion, and wear at the micro- and nano-scale becomes more critical for MEMS/NEMS devices. Ultrananocrystalline diamond (UNCD) films synthesized using argon-rich Ar/CH4 plasmas, exhibit high stiffness, strength and fracture toughness, and surface chemical inertness, making UNCD an excellent candidate material for MEMS. We have applied Auger electron spectroscopy (AES), near-edge x-ray absorption fine structure (NEXAFS), x-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) to understand the surface chemical bonding, micro/nanostructure as well as adhesion and frictional properties of the top and underside UNCD surfaces. We will discuss how these properties are influenced by the initial nucleation pre-treatment and surface chemistry of the UNCD, and how one can engineer the surface to obtain low adhesion and frictional properties. Our results indicate that H-terminated UNCD exhibits extremely low adhesion, essentially indistinguishable from that of H-terminated single crystal diamond and far lower than silicon.
Summary: Fabricating MEMS or NEMS devices that involve rolling or sliding contacts with reasonable operational life is still a challenging task due to tribological issues. We will also discuss the relationship between nanotribological behavior, surface morphology, and surface chemistry of UNCD, and how this relates to UNCD MEMS performance.
