Nitrogen-induced nanometre-scale faceting of Cu(410)

Scanning tunnelling microscopy has been used to investigate the morphological and atomic-scale structural changes to a Cu(410) surface induced by adsorbed atomic nitrogen. This (100) vicinal face is found to restructure to form ordered arrays of (100) nanofacets, separated by double-height steps of local (210) or (310) orientation, with a periodicity of approximately three times that of the step spacing of the original (410); step bunches to produce (210) and (310) nanofacets restore the correct average orientation. The (100) nanofacets show a c(2×2) structural phase similar to that found for N adsorption on extended Cu(100) surfaces, but do not show the novel c(2×2)-N 50 Å island ordering seen on Cu(100), usually attributed to the role of local compressive surface stress. However, single atomic steps occur across the (100) nanofacets at 100–200 Å intervals, and this modified morphology is attributed to the role of the narrow facets in allowing lateral strain to reduce the compressive stress. The absence of (110) facets associated with full agglomeration of surface steps is discussed in terms of the structure of the pseudo-(100) outermost layer of the (2×3) reconstruction which characterises the adsorption of N on extended Cu(110) surfaces.