The kinetics of oxygen-induced faceting of Cu(115) and Cu(119) surfaces

Faceting of the vicinal Cu(115) and Cu(119) surfaces due to oxygen adsorption was studied by scanning tunelling microscopy (STM). Both surfaces reconstruct into two kinds of {104}-type facets and a third facet determined by the macroscopic surface orientation. This third facet is {113}-oriented for Cu(115) and {100}-oriented for Cu(119). On all facets CuOCu chains are developed that are energetically favored. On oxygen-saturated surfaces (exposure between 100 and 1000 L) the facet size is determined by the formation kinetics, as could be shown by varying the sample temperature during adsorption (between 410 and 620 K) or by varying the adsorption rate (oxygen pressure between 5.6×10−9 and 2×10−5 mbar). This facet size dependence can be formally described by equations derived for nucleation and growth mechanisms. But experiments with lower oxygen exposure (10 to 20 L) indicate that facet formation proceeds in several steps. In that case, small (100)-facets along the step edges can be seen between regions with final reconstruction. An atomistic model for this facet formation is proposed.