1-D nanostructures grown on the Si(5 5 12) surface

We have used scanning tunneling microscopy (STM) to study the growth behavior of noble metals deposited on the high-index Si(5 5 12) surface. This unique surface is tilted 30.5° down from (0 0 1) and forms a single-domain reconstruction composed of row-like structures. When low coverages (<0.25 ML) of noble metals such as Ag and Au are deposited onto Si(5 5 12) and moderately annealed (∼450°C), they form overlayer “nanowires” with the periodicity of the Si surface (5.4 nm). It is the preferential reactivity of the underlying Si row structures that results in this well-ordered growth behavior. At higher coverages and temperatures, however, these metals can cause significant restructuring of the surface that leads to the creation of neighboring facet planes. Ag forms nanoscale sawtooth facets at coverages above 0.25 ML, but they are relatively narrow (5–10 nm wide) and do not cause the surface to undergo a dramatic restructuring. In contrast, Au deposition induces significant faceting of the surface, resulting in the formation of (1 1 3), (2 2 5), (3 3 7), (5 5 11), or (7 7 15) facet planes composed of periodic 1-D nanostructures.