AVS 46th International Symposium
    Nanometer-scale Science and Technology Division Monday Sessions
       Session NS1-MoA

Paper NS1-MoA2
Contact Hysteresis, Friction and Conductance of Self-Assembled Monolayers on Au

Monday, October 25, 1999, 2:20 pm, Room 612

Session: Nanoscale Tribology and Adhesion
Presenter: J.D. Kiely, Sandia National Laboratories
Authors: J.D. Kiely, Sandia National Laboratories
J.E. Houston, Sandia National Laboratories
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We have investigated the relationship between friction and the mechanical, electrical and chemical properties of self-assembled monolayers of hexadecanethiol on the Au(111) surface using the interfacial force microscope. We find a very low friction coefficient for freshly prepared films with a direct correlation of the frictional force with the contact hysteresis, i.e., the energy dissipated in the film during a loading/unloading cycle. In addition, the film conductance is found to increase exponentially with the applied film stress under loading. Above film stresses of about 4 Gpa, the film compliance and frictional force rise sharply while the conductance remains log linear. To simulate aging in a laboratory environment, we have oxidized films by direct exposure to ozone and find that the frictional force, conductance and hysteresis all rise dramatically. We discuss these results in terms of the known properties of the monolayer films and the findings of previous work on the effects of oxidation by ozone exposure. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000.