Self-Assembled Parallel Mesoscopic Pb Wires on Vicinal Si(111)

The work presents a novel method of production of mesoscopic metallic wires on semiconducting surfaces. Making use the self-assembly phenomenon, arrays of extremely long and perfectly parallel mesoscopic Pb-wires on vicinal Si(111) substrates are formed and studied in UHV conditions. Before deposition of Pb a uniform distribution of monoatomic steps and terraces was induced by formation of Au chains running along step edges. The wires growing on the substrates held at temperatures close to the room temperature reach up to 8 µ length. A reflection high electron energy diffraction experiment shows that the wires laying on Si(533) along the step edges have triangular cross-section determined by (111) and (100) facets of Pb. Scanning tunneling microscopy images collected at low temperatures have enabled us to determine details of the wires shape and morphology of the substrate. The width of the wires was approximately equal to 60 nm whereas their height was about 10 nm. The observed strong growth anisotropy is attributed to step edge barriers and high Pb mobility on the smooth Si(111) narrow terraces that form vicinal surfaces and the anisotropic strain due to large misfit between Pb and Si lattices.