Faceting and reconstruction of stepped Au(111)

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Abstract
We present the results of an x-ray scattering study of the structure and morphology of a stepped Au(111) surface between 480 and 1225 K. At the highest temperatures studied, the surface phase separates to form three distinct orientational phases, each of which is reconstructed. These consist of (111) facets and two stepped phases, the latter differing in the polar and azimuthal orientations of their surface normal directions. The temperature-dependent reconstructions of the (111) facets are similar to those observed on the Au(111) surface. Specifically, the (111) facets exhibit a discommensuration-fluid phase above 700 K and a chevron phase, consisting of ordered discommensurations and kinks, below. The transformation from the discommensuration fluid phase to the chevron phase is remarkably slow, requiring on the order of tens of hours to complete. At the highest temperatures, the terraces of both stepped domains are uniaxially compressed, resulting in a series of well-ordered linear discommensurations. In one of the stepped phases the discommensurations intersect the step edges at 60°, while in the other, they lie orthogonally to the step edges. On cooling, the latter stepped phase becomes unreconstructed below 985 K and vanishes below 775 K, resulting in a surface comprised of (111) facets in coexistence with a single reconstructed stepped phase.