Oxygen-induced step-edge faceting; a precursor to (410) planar faceting of Cu(100) vicinal surfaces

Scanning tunneling microscopy has been applied to an atomistic scale investigation of the oxygen-induced restructuring of a Cu(100) vicinal surface, close to (610) but with average step orientations 10° away from [001]. The initial changes upon oxygen adsorption are found to be step-edge faceting to [001] and [010], and [001] step coalescence to form small (410) facets. Annealing enlarges these (410) facets while the much shorter [010] steps coalesce to form (401) facets. The implied strong energetic favouring of 〈100〉 step-edges in the presence of oxygen is attributed to the formation of CuOCuO linear chains, known to be the stable element of oxygen-induced reconstruction of the (110) and (100) copper surfaces.