FACETING AND RECONSTRUCTION OF STEPPED AU(111)

We present the results of an x-ray scattering study of the structure a nd 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. T hese consist of (111) facets and two stepped phases, the latter differ ing in the polar and azimuthal orientations of their surface normal di rections. The temperature-dependent reconstructions of the (111) facet s are similar to those observed on the Au(111) surface. Specifically, the (111) facets exhibit a discommensuration-fluid phase above 700 K a nd 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 o f hours to complete. At the highest temperatures, the terraces of both stepped domains are uniaxially compressed, resulting in a series of w ell-ordered linear discommensurations. In one of the stepped phases th e discommensurations intersect the step edges at 60 degrees, while in the other, they lie orthogonally to the step edges. On cooling, the la tter stepped phase becomes unreconstructed below 985 K and vanishes be low 775 K, resulting in a surface comprised of (111) facets in coexist ence with a single reconstructed stepped phase.