Tuesday, 12 October 2004 - 9:40 AM

This presentation is part of : Wear and Tribology

Atomic force microscopy/nanotribology studies of simultaneous application of chemical agents and mechanical stress

Tom Dickinson, Washington State University, Washington State University, Department of Physics, Pullman, WA 00164-2814

We describe results of fundamental tribochemical studies of the simultaneous application of chemical agents and mechanical stress applied between a model single asperity and a solid surface at the nanometer size scale. We show the consequences of combining highly localized mechanical stress (due to contact with an atomic force microscope--AFM tip) and exposure to aqueous solutions. In many respects, our results share similar behavior to stress-corrosion crack growth in materials such as silica glass. Also, our experiments simulate many features of a single particle-substrate-slurry interaction in Chemical Mechanical Planarization-CMP (the method for repeated generation of flat surfaces required in the numerous lithography steps used in device manufacturing on silicon wafers). In particular we show quantitative, correlated data on the wear occurring on both surfaces and how wear at the nanometer size scale influences friction, contrary to theories of macroscopic friction. We examine surfaces of inorganic single crystals, glasses, and silicon nitride as well as strongly adhering particles on glass substrates. We also present results on tip induced recrystallization (at small normal forces) and unique patterning produced by scanning in super-saturated aqueous solutions. Examples on biomineral surfaces [calcite (CaCO3) and brushite (CaHPO4.2H2O)] are presented where monolayer growth can be controlled and induced by the tip at crystal step edges and at the edges of rhombohedral etch pits;. growth occurs only in the area of scanning. Growth rates at particular steps proved to be strongly depend on step orientation. Models are presented to explain these observed nanometer scale surface modifications.

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