We present scanning tunnelling microscopy results of thin dysprosium silicide films grown on Si(001) 21. At submonolayer coverages, up to 2000 Å long wires are formed in the (110) direction of the Si(001) surface. Depending on Dy exposure and annealing conditions, both wire assemblies and free-standing wires can be grown. At higher coverages, three-dimensional clusters with rectangular shapes are formed.

Free-standing dysprosium–silicide nanowires can be formed on Si(001) by self assembly. It is shown that the wires consist of anisotropically strained hexagonal DySi2 with the c axis aligned perpendicular to the wires. The surface is characterized by a 2×1 reconstruction due to the formation of Si dimer chains.

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Dielectric and optical properties of epitaxial rare-earth scandate films and their crystallization behaviorWe present an investigation of Gd, Dy, Er, and Lu silicides epitaxially grown on n-type Si͑111͒ using scanning-tunneling microscopy, low-energy electron diffraction, and core-level photoemission. With varying silicide film thickness, we observe structurally, electronically, and chemically different silicide phases. In particular we found that the Si-2p photoelectron spectra from monolayer silicides are different from those at higher coverages. This observation is attributed to the structure of the layered hexagonal silicide, with a Si vacancy lattice only present in case of multilayer films. Furthermore, we observe peculiar electronic properties: An extremely low band bending is found in the monolayer range, with a Fermi-level position of only 0.08Ϯ0.05 eV below the conduction-band minimum of silicon, representing the lowest value ever observed on n-type silicon. With increasing coverage, a final Schottky-barrier height of 0.32Ϯ0.05 eV is obtained. This behavior is interpreted as a consequence of the developing metallicity of the silicide overlayer and will be discussed in the framework of theoretical models for Schottky-barrier formation.

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