Nano-faceting of fcc(1 1 0) surfaces controlled by adsorbates and atom deposition or removal

(1 1 0) surfaces of most fcc metals are only marginally stable against faceting into (1 1 1) orientations. Trace concentrations of adsorbates (surfactants) that prefer (1 1 1) over (1 1 0) facets can tip the balance and favor faceting of all or part of the (1 1 0) surface. The growth of such facets is impeded by island and vacancy-island nucleation barriers. However, during atom deposition or etching these barriers are reduced. Growth or removal conditions and facet stabilizing surfactant concentrations control the evolving faceted nano-patterns. Recent observations of hut-shaped nanocrystals formation on Al(1 1 0) are consistent with this model.