The transport processes that occur at small length scales are greatly influenced by interfacial and intermolecular forces. Surface roughness at the nanoscale generates additional intermolecular interactions that arise due to the increased surface area. In this work, we have experimentally studied how the magnitude as well as the shape of surface roughness influences the microscale transport processes that occur in the contact line region of a liquid corner meniscus. The surface roughness contribution to the interaction potential was calculated and a direct relationship between the wetting properties of the liquid and the underlying surface properties was obtained. Since the underlying roughness alters the surface potential, the shape of the meniscus and in turn, the resulting capillary and disjoining pressure forces also changed. Atomic force microscopy was utilized to obtain a detailed characterization of the shape of the prepared surfaces. Surface morphology features were obtained from a height-height correlation function. These features were related to the wetting and transport properties of the meniscus at the contact line. Finally, the modified capillary and disjoining pressure forces on the structured surfaces were observed to influence the evaporative heat transfer from the corner meniscus.
The surface chemistry associated with a-Si:H growth by plasma-enhanced chemical vapor deposition is unique in that the hydrogen-passivated surface results in a low threshold energy for surface diffusion relative to the cohesive energies of the material. We show that helium ion bombardment enhances the hopping rate of loosely bound film precursors without substantially affecting the condensed a-Si:H material. Our investigative approach consists of examination of the temporal evolution of the surface topography under different substrate bias conditions. Without biasing the substrate, the surface morphology becomes unstable, producing mounded-type structures, consistent with shadowing growth instability. Biasing the substrate suppresses these instabilities and allows an initially rough a-Si:H surface to be smoothed during subsequent deposition.
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