Dynamic Probes of Tribological Processes

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0116169DickinsonThese studies focus on fundamental mechanisms and applications of nanometer scale surface manipulation involving combined stimuli, where the tip of a scanning force microscope stimulates the surface in the presence of an aggressive chemical solution. These combined stimuli can make and break bonds and reorganize material on surfaces of single crystals, glasses, and polymers in a highly localized fashion. We will examine the role of crystalline and other structural defects (e.g., steps, kinks, vacancies, and nanostructures generated by the tip) in dissolution and growth to identify the rate limiting steps (with and without stimulation by the SFM tip) and how they depend on stress, solution chemistry, and temperature. These results will be related to fundamental physical and chemical parameters governing dissolution and growth, such as activation energies and volume/entropic factors. We also will examine how the apparently random mechanical vibrations in cantilevers during scanning might be related to transient surface phenomena in supersaturated solutions. These studies have considerable promise in the development of new methods for generating atomically flat surfaces, constructing novel nanometer structures, and producing textured surfaces for bonding and chemically active arrangements. The studies also support atomic level understanding of the technologically important process of chemical mechanical polishing (CMP), where the SFM tip serves as a model abrasive particle. Sensor development, MEMS, and development of new biologically active substrates and surfaces will benefit from the improved molecular-level understanding of dissolution and growth resulting from this work. ***