An X-ray scattering study was made of the structure and morphology of a stepped (111) surface at temperatures of between 480 and 1225K. At the highest temperature, the surface phase separated to form 3 distinct orientational phases; each of which was reconstructed. These consisted of (111) facets and 2 stepped phases, in which the latter differed with regard to the polar and azimuthal orientations of their surface normals. The temperature-dependent reconstructions of the (111) facets were similar to those which were observed on the (111) surface. In particular, the (111) facets exhibited a discommensuration fluid phase at temperatures above 700K, and a chevron phase which consisted of ordered discommensurations and kinks at lower temperatures. The transition from the discommensuration fluid phase to the chevron phase was remarkably slow, and required some days to complete. At the highest temperatures, the terraces of both stepped domains were uniaxially compressed, and this resulted in a series of well-ordered linear discommensurations. In one of the stepped phases, the discommensurations intersected the step edges at 60 while, in the other phase, they were orthogonal to the step edges. Upon cooling, the latter stepped phase became unreconstructed at temperatures below 985K and vanished at temperatures below 775K. This resulted in a surface that consisted of (111) facets which coexisted with a single reconstructed stepped phase.

G.M.Watson, D.Gibbs, S.Song, A.R.Sandy, S.G.J.Mochrie, D.M.Zehner: Physical Review B, 1995, 52[16], 12329-44