Terrace width dependence of cobalt silicide nucleation on Si(111)-(7×7)

We have studied the size, shape transition, and nucleation sites of self-assembled cobalt silicide clusters on Si(111)−7×7 using scanning tunneling microscopy. Step decoration of solid-phase-epitaxy grown clusters (350–1000 °C) is observed on surfaces with narrow terrace widths (25–40 nm). Experiments repeated on surfaces with wide (>70nm) terraces reveal significant differences with respect to shape, size, and growth morphology; a bimodal size distribution is observed due to cluster shape transition from irregular clusters to flat-top islands. The control of silicide island nucleation could have potential applications in electrode formation for molecular electronics and nanodevice fabrication.