The growth of Cu on the stable Si(5 5 12) clean surface has been studied as a function of coverage and temperature using scanning tunneling microscopy. Similar to previously studied group 18 metals, Cu produces overlayer "nanowires" at lower growth temperature (<500 degreesC), where the 5.4 nm periodicity of the (5 5 12) surface is maintained. At higher temperatures (> 500 degreesC), however, the underlying Si surface is disrupted and Cu induces faceting to the nearby (113) plane. At coverages above approximately 0.5 ML, the surface rearranges-to form sawtooth facets composed of wide (113) planes opposed by narrow (111) segments. The (113) planes show a Cu-induced 2 x 2 surface reconstruction that incorporates a large number of domain boundaries. We have also studied the O-2 reactivity of the Cu-induced (113)/(111) sawtooths. At temperatures above 650 degreesC, the sawtooths are gradually etched away to produce trapezoidal islands. The density of these islands, decreases with increasing temperature, providing a possible route for the controlled fabrication of such nanostructures. (C) 2003 American Vacuum Society.