IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Tribology Wednesday Sessions
       Session TR+MM-WeA

Paper TR+MM-WeA7
Superconductivity Dependent Friction of Adsorbed Monolayers on Pb(111)

Wednesday, October 31, 2001, 4:00 pm, Room 132

Session: Nanotribology
Presenter: J. Krim, North Carolina State University
Authors: J. Krim, North Carolina State University
A. Mayer, North Carolina State University
L. Wagner, North Carolina State University
Correspondent: Click to Email
In order to gain a fundamental understanding of friction, one must understand, at the molecular level, how the energy associated with the work to overcome friction is converted to heat. Such knowledge is key to understanding the rate at which an interface will heat, and in addition how chemical reactions and other physical processes triggered by heat will be affected by friciton. One of the simplest possible geometries in which friction can occur, and thus be studied, is that of a fluid or crystalline monolayer adsorbed on an atomically flat surface. This geometry is experimentally accessible to experiments with a Quartz Crystal Microbalance (QCM), to numerical simulation techniques, and to analytic theory. A recent QCM experiment@footnote 1@ sought to explore the nature of electronic contributions to friction by measuring the friction associated with nitrogen monolayers sliding on Pb substrates as the temperature passed through the superconducting transition at 7.2K. The work inspired a number of subsequent theoretical and experimental efforts, which yielded contradictory results. A major complication associated with the Ref. 1 result arose from the fact that the data were reported for Pb substrates which had been exposed to air. We have thus repeated the measurements on Pb substrates which have been prepared in situ for both nitrogen and rare gas monolayers. The latter have been predicted by some theories to exhibit no dependence on the superconducting state of the sample. We present these results and compare them to the various conflicting theories. @FootnoteText@@footnote 1@ A. Dayo, W. Alnasrallah and J. Krim, Phys. Rev. Lett. vol 80, 1690 (1998) Work funded by NSF.