AVS 50th International Symposium
    Nanometer Structures Wednesday Sessions
       Session NS-WeA

Paper NS-WeA9
The Wear of NaCl in Humid and Anhydrous Environments

Wednesday, November 5, 2003, 4:40 pm, Room 308

Session: Nanotribology
Presenter: L.J. Whitman, Naval Research Laboratory
Authors: P.E. Sheehan, Naval Research Laboratory
L.J. Whitman, Naval Research Laboratory
Correspondent: Click to Email
A recent report on the mechanism of dip pen nanolithography (DPN)@footnote 1@ indicated that wear on NaCl reveals the presence of a residual meniscus even under dry nitrogen. We have studied the wear of a NaCl single crystal by an AFM tip as a function of environmental humidity. In an anhydrous nitrogen environment, we find that the wear mechanism was not meniscus-based but rather mechanical, with the wear rate well-described by a thermal-activation model. By examining the wear track while varying both the temperature and the load, the activation volume and the activation energy could be measured. Introducing a slight amount of water into the anhydrous system dramatically changed the wear mechanism. In this case, salt dissolution and reformation occur, creating islands that are several atomic layers thick with clearly-observable step edges. Interestingly, the morphology of the islands indicates that they are fluid while in contact with the AFM tip and presumably its water meniscus; however, when the AFM tip is quickly removed, the islands solidify and can be imaged by a rapidly moving tip. This observation may lead to a method of patterning NaCl on the nanometer-scale. @FootnoteText@@footnote 1@ Rozhok, S.; Piner, R.; Mirkin, C. A.; J. Phys. Chem. B. (2003) 107 751-757.