AVS 51st International Symposium
    MEMS and NEMS Monday Sessions
       Session MN-MoM

Paper MN-MoM6
Characterization of Nanotribological Properties and Surface Chemistry of Advanced Nanostructured Carbon Materials for MEMS and NEMS Applications

Monday, November 15, 2004, 10:00 am, Room 213C

Session: Processing and Characterization for MEMS and NEMS
Presenter: A.V. Sumant, University of Wisconsin-Madison
Authors: A.V. Sumant, University of Wisconsin-Madison
D.S. Grierson, University of Wisconsin-Madison
J.E. Gerbi, Argonne National Laboratory
J.P. Birrell, Argonne National Laboratory
J.A. Carlisle, Argonne National Laboratory
O.H. Auciello, Argonne National Laboratory
T. Friedmann, Sandia National Laboratories
J.P. Sullivan, Sandia National Laboratories
R.W. Carpick, University of Wisconsin-Madison
Correspondent: Click to Email
Despite rapid advances in micro- and nanofabrication technologies, the implementation of reliable, high endurance devices that involve sliding contacts remains elusive. At small length scales, device properties are dominated by surface chemistry rather than bulk properties, and therefore materials with superior tribological properties and optimized surface chemistry are needed. Ultrananocrystalline diamond (UNCD) and tetrahedra amorphous carbon (taC) thin films have exceptional physical, chemical and tribological properties at the macroscale (nearly equivalent to those of single crystal diamond) and are being considered promising materials for the fabrication of high performance MEMS devices. However, little is known about the surface chemistry of these materials, and how it affects their nano- and micro-scale tribological performance. We have developed detailed methodologies to characterize nanotribological properties and surface chemistry of UNCD and taC at the tribologically relevant interface by using a combination of near-edge X-ray absorption fine structure spectroscopy (NEXAFS), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). We show that the surface chemistry, sp2-sp3 ratio, and nanoscale friction and adhesion can be different on the etched underside of the film (the side which becomes exposed and makes tribological contact after a MEMS release process) as compared with the top side of the film. We also discuss the effect of hydrogen plasma treatment, which in the case of UNCD renders the surface extremely inert and chemically pure, and reduces nano-scale friction and adhesion dramatically. Adhesion, as measured with tungsten carbide AFM probes, is reduced to the van der Waals limit indicating full saturation of dangling surface bonds and elimination of surface contaminants.