Pb nanowires formed on the stepped surface of Si(557) were recently reported by Tegenkamp to exhibit an intriguing insulator-to-metal transition upon cooling with the metallic character persistent to 4 K. High-resolution photoemission spectroscopy and low-energy-electron diffraction (LEED) are applied to systematically investigate the phase formation of Pb on Si(557) and to disclose its overall structural and electronic properties. Through LEED, we find two anisotropic phases around one monolayer coverage in addition to the well-known two-dimensional Pb overlayer phases observed on a flat Si(111) surface. In particular, the anisotropic phase denoted as α×2 with a 4 2 3 ×2 periodicity (×2 along step edges) has a good long-range order and is thought to be due to an ordered nanowire array. In Si 2p spectra, an extremely narrow line shape and distinct surface components are identified for the α×2 phase supporting its good structural order. The Pb 5d core-level spectra indicate that the α×2 phase consists of a single-dense Pb layer with two distinct Pb sites. The metallic nature of this phase is indicated by the asymmetric line shapes of Pb 5d and Si 2p and the finite density of states at Fermi level in valence-band photoemission.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 2007 May 18|
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics