Scanning tunneling microscopy studies of the Cu:Si(5 5 12) system

Abstract

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 IB metals, Cu produces overlayer “nanowires” at lower growth temperature (<500 °C), where the 5.4 nm periodicity of the (5 5 12) surface is maintained. At higher temperatures (>500 °C), 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 2×2 surface reconstruction that incorporates a large number of domain boundaries. We have also studied the O2 reactivity of the Cu-induced (113)/(111) sawtooths. At temperatures above 650 °C, 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.