AVS 58th Annual International Symposium and Exhibition
    Tribology Focus Topic Thursday Sessions
       Session TR-ThA

Paper TR-ThA9
A Study of Sliding Friction Across Velocity Regimes for Alternative MEMS-type Interfaces using Atomic Force Microscopy and Combined Nanoindentation / Quartz Microbalance

Thursday, November 3, 2011, 4:40 pm, Room 111

Session: Advanced Tribological Materials
Presenter: Brian P. Borovsky, Saint Olaf College
Authors: N. Ansari, Auburn University
S. Barkley, Luther College
C. Bouxsein, Saint Olaf College
M. Deram, Saint Olaf College
N. Eigenfeld, Saint Olaf College
O. Matthews, Luther College
A. Poda, Auburn University
W.R. Ashurst, Auburn University
E.E. Flater, Luther College
B.P. Borovsky, Saint Olaf College
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As mechanical devices have shrunk to microscopic sizes, the need for a more fundamental understanding of friction and other surface phenomena has become urgent. While the emerging technology of microelectromechanical systems (MEMS) shows promise as the mechanical counterpart to integrated circuits, progress remains slow as structural materials and lubricant strategies continue to be developed. We report on the results of a collaborative effort to study the frictional properties of organic monolayers deposited on metal oxide surfaces. These interfacial systems have the potential to offer an alternative to silicon-based device fabrication. Both a nanoindenter-quartz crystal microbalance (NI-QCM) as well as an atomic force microscope (AFM) in lateral force mode have been used to perform tribological experiments at sliding velocities spanning the range from microns per second to meters per second. Our studies have investigated two different self-assembled monolayers chemisorbed onto aluminum oxide surfaces with realistic contact roughnesses and sizes: octadecylphosphonic acid (ODP) and octadecyltrichlorosilane (OTS). Both monolayers are observed to exhibit substantially reduced friction as compared to the bare interface, at both low as well as high sliding speeds. However, the films appear to fail upon exceeding a threshold contact pressure. We compare the tribological responses of the bare and monolayer coated interfaces of different systems and discuss insights into the molecular-level mechanisms responsible for the observed behaviors.