Rational nanoscale control of interfacial structure and dynamics.

摘要

The work discussed in this thesis focuses in general on exploiting new understanding of phenomena at the nanoscale for control of interfacial properties. Specifically, experiments were performed using two surfaces: stepped Ni(977) and flat Au(111), each with its own interesting and unique characteristics. An array of surface science techniques were used to provide a multifaceted and complimentary perspective. Helium atom scattering served as the primary tool but scanning tunneling microscopy, atomic force microscopy, electron diffraction, and electron spectroscopy were also used extensively. These surface probes, using both real- and reciprocal-space methodologies, allow for study of both local and surface-averaged chemical physics.; Salient results from these studies include the discovery that vicinal surfaces can be used as a natural template for both known and novel structures ranging from the scale of Ångstroms to nanometers. The order-disorder transition for (2 x 2)-2H hydrogen was found to be 40 K higher on Ni(977) compared to the flat analogue—Ni(111). Furthermore, this step-stabilized phase was used to form nanoscale corrals that templated a xenon overlayer with unusual (2 x 2) symmetry. A series of experiments involving adsorption and absorption of oxygen, in concert with Monte Carlo simulations, revealed three principal results: a new (n x 2)-O phase created by step confinement, a surprisingly strong influence of oxidation history on future oxygen-driven reconstruction, and a predictive understanding of the kinetics associated with defect formation in Ni(977) step doubling.; A second stage of studies, carried out on Au(111), furthered the understanding of the technologically and biologically significant process of self-organization. A dispersionless molecular vibration within a striped phase decanethiol self-assembled monolayer was discovered at ±8 meV, and it was demonstrated that adsorption of low-density thiolate monolayers does not deconstruct the substrate, as has been commonly suggested. Lastly, kinetics of the phase segregation of two-component self-assembled monolayers were investigated using an alkyl fluoroalkyl disulfide. Unlike slightly shorter analogues that form phase domains on the scale of 100 nm, the system studied in this work separated into islands on the scale of 10 nm suggesting a strong barrier to surface diffusion within the monolayer.