AVS 46th International Symposium
    Nanometer-scale Science and Technology Division Tuesday Sessions
       Session NS1-TuM

Paper NS1-TuM11
SFM Studies of Environmentally Assisted Detachment of Strongly Adhering Particles@footnote 1@

Tuesday, October 26, 1999, 11:40 am, Room 612

Session: Nanomechanics
Presenter: R.F. Hariadi, Washington State University
Authors: R.F. Hariadi, Washington State University
S.C. Langford, Washington State University
J.T. Dickinson, Washington State University
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The production of flat surfaces is often hindered by small particles that adhere strongly to the substrate. We have undertaken a model study of the detachment of sub-micron particles via tribological interactions. Scanning force microscope, silicon nitride tips (typically about 50 nm in diameter) are used to apply stress to 10-100 nm single crystal NaCl crystallites grown on and strongly bonded to soda-lime glass substrates. In most experiments, the applied force is a combination of a compressive normal force and a lateral force, both measured simultaneously. In a time- and spatially-resolved fashion, we apply the stress and measure the response (e.g., detachment). Only the smallest particles can be detached in dry air. However, as the relative humidity (RH) is increased, the crystallites detach at considerably lower stresses. We also observe particle reattachment as a function of time and RH; all reattachments show only a fraction of the original adhesion. We model the detachment process in terms of environmentally enhanced crack growth (due to moisture); when the crack reaches a critical length that depends on particle size, catastrophic interfacial fracture follows. Numerical estimates of the necessary work of adhesion, based on a network of ions interacting via polar forces with the glass, are described. These calculations are in reasonable agreement with our data. @FootnoteText@ @footnote 1@Work supported by the NSF Surface Engineering and Tribology Program under Grant CMS-98-00230.