Pb nanowires on vicinal Si(111) surfaces: Effects of refacetting on transport

The conductance of Pb wires grown by self-assembly on Si(557) has been studied in detail as a function of coverage and of the facet structure. Only for 1.31 ML, corresponding to one physical monolayer on the terraces (steps not covered with Pb), and a perfectly ordered wire array along the [(11) over bar2] direction quasi-onedimensional (1D) transport along the [(11) over bar2] direction is found, corroborating the model of one-dimensional band filling in an adsorbate induced (223) facet structure. The transport results recently shown by Morikawa et al. [Phys. Rev. B 82, 045423 (2010)] can also reproduced by our group. In contrast to what was claimed by them, our results clearly show that either a too small coverage or structural imperfections of the surface are responsible for a metal-insulator transition around 140 K irrespective of the crystallographic direction. The variety of different transport scenarios found is caused by strong adsorbate-induced refacetting into an electronically stabilized (223) orientation, which differs from the macrosocopic orientation of the substrate. The crucial interplay between structure and filling factor explains the extremely small parameter window in which the 1D transport channel can be observed.