(161e) Disparity in Adsorption of Octadecyltrichlorosilane Islands On Rough Silicon Oxide Surfaces

The details of molecular assembly on topographical asperities, plays an important role in systems such as MEMs where SAM coated asperities must resist wear and adhesion during controlled or accidental contact during device operation. Many discrepancies associated with tribological performance have been identified as SAMs have been applied to surfaces of varying topographical complexity. SAM growth kinetics and interfacial properties as deposited on MEMs devices are often inferred from information learned on smooth surfaces. Questions remain as to whether the topographical morphology of the MEMs device will play an important role in the quality of improvement afforded from a deposited SAM. Research has shown that monolayers need to maintain a specific packing density and molecular orientation as deposited on surfaces of low roughness in order to provide a high tribological response. This research focuses on the interfacial structure of self-assembled coatings as influenced by surface topography and its implications toward tribological performance. Emphasis is placed on OTS islands produced from the (LC) phase due to the fact that this phase has shown the greatest propensity for friction improvement. Densely packed OTS islands resulting from low temperature deposition conditions are deposited onto native silicon oxide surfaces and onto silicon oxide surfaces created via molecular vapor deposition (MVD). The utilization of an MVD silica surface allows for an examination of a reactive silica surface with a variable degree of surface roughness as well as different topographical asperities (i.e. peak sizes, peak shapes). This silicon surface due to its amorphous nature allows for a true investigation of adsorption of OTS islands as influenced by topographical asperities eliminating the complexities associated with a polysilicon surfaces often influenced by dopant levels and water accumulation at crystal grain boundaries. In order to analyze the adsorption of the OTS islands and provide topographic resolution for AFM imaging the samples are exposed to a dilute etchant which removes only the MVD deposited silica that is not ?protected' by densely packed OTS islands.

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