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We report on the atomic structure and electronic properties of self-organized dysprosium and erbium silicide nanowires on Si͑557͒, studied using scanning tunneling microcopy and angle-resolved photoelectron spectroscopy. The nanowires were prepared by deposition of different rare earth amounts and subsequent annealing for silicide formation. Due to the stepped structure of the Si͑557͒ surface, nanowires form along the step edges, showing a variety of structurally and electronically different types, depending on the preparation conditions. At submonolayer dysprosium coverages, different chainlike structures dominate, showing one-dimensional dispersion with half-metallic properties. These nanowire regions are separated by 7 ϫ 7 reconstructed Si͑111͒ facets or submonolayer dysprosium silicide patches on these facets. At monolayer coverages, in contrast, mainly nanowires with lengths exceeding 1 m and widths of a few nanometers are found, forming on the ͑111͒ facets of the Si͑557͒ surface. Their electronic properties are characterized by a two-dimensional band structure with strong dispersion both parallel and perpendicular to the nanowires and clear metallic behavior, and it is demonstrated that they are formed from hexagonal DySi 2 monolayers. In the case of thicker silicide layers, metallic nanowires form again on the Si͑111͒ facets, but with clear structural and electronic characteristics of hexagonal Dy 3 Si 5 multilayers. At these coverages, additional structures are found, which show an intense signal in the photoelectron spectroscopy data. Related experiments on the growth of erbium silicides indicated the formation of very similar nanowire structures.

The self-organized growth of dysprosium silicide nanowires on Si(557) has been studied using scanning tunneling microcopy and angle-resolved photoelectron spectroscopy. The nanowires grow on the (111) facets of the Si(557) surface with lengths exceeding 1000 nm and widths of 3–5 nm. Their metallic electronic structure shows a two-dimensional behavior with a strong dispersion, which is both parallel and perpendicular to the nanowires. For Dy coverages of around 2 Å, it is demonstrated that the nanowires consist of hexagonal DySi2 monolayers, while at higher coverages they are predominantly formed from Dy3Si5 multilayers.

The (111)-2×1 surface of in situ cleaved heavily P-or B-doped Si is investigated by scanning tunnelling microscopy and spectroscopy at room temperature and at low temperature. P atoms have been identified on different sites of the Si(111)-2×1 surface by their characteristic voltage-dependent contrast for positive as well as negative buckling of the π-bonded chains. The distributions of dopants per surface area and of nearest-neighbour distances are found to be in agreement with a random arrangement of dopants in Si up to doping levels well above the metal-insulator transition. In addition, P atoms have been identified by their depth-dependent contrast down to the third layer beneath the surface with a volume density in agreement with the bulk doping density. The random electronic disorder supports the view of an Anderson transition driven by disorder close to the critical concentration or critical uniaxial stress.