The plasmon dispersion in arrays of nanowires of Pb close to an average Pb coverage of one monolayer was determined on the Si(557) surface using electron energy loss spectroscopy with both high energy and momentum resolution. While we find purely one-dimensional (1D) plasmon losses at a Pb concentration of 1.31 monolayers (ML), measured with respect to the Si(111) surface concentration, the 1.2 and 1.4 ML coverages exhibit wavelength-dependent transitions from 1D to anisotropic 2D properties. However, due to the high anisotropy in the system at all coverages, the dispersion curves exhibit 1D characteristics in both directions. This behavior seems to be related to the Pb-induced refacetting of the Si(557) surface, which depends on Pb coverage. It changes both effective system sizes and coupling strength between miniterraces.

The fabrication and characterization of metallic nanometer-sized gaps suitable for conductivity measurements of single molecules were studied. Controlled gap formation by electromigration (EM) is demonstrated in contiguous and ultrathin Ag structures wetting the Si(100) substrate. The gaps obtained are in the range of nanometers or even subnanometers, as revealed by lateral conductivity measurements and scanning tunneling microscopy carried out under ultrahigh vacuum conditions. Annealing to 300K closes the gap by enabling surface diffusion of Ag, and another cycle of opening by EM at 80K can be performed. The functionality of the contacts is demonstrated by insertion of ferrocenedithiol molecules into the gap.

The low coverage phase transitions of the p(8ϫ1) and the p(5ϫ1) chain structures of the Sr/Mo͑112͒ system have been investigated with low-energy electron diffraction ͑LEED͒ at constant coverages. It turns out that both structures show similar physics. They first undergo depinning phase transitions at temperatures just below 100 K into striped domain wall structures. The domain wall lattice shows continuous melting at temperatures between 197 and 218 K. Coupling between the adsorbate chains can be described by the potential created by adsorbate-induced charge density waves involving surface states. Within this model domain wall formation appears as thermal excitation of stacking faults on a discrete lattice. For the p(5ϫ1) structure, domain wall formation energies of approximately 65 and 38 meV have been derived for heavy and light walls, respectively, from a fit to the experimental data of depinning.

We explored the structural limits of unconventional electron-beam lithography by directly writing with an electron beam into ultrathin SiO2 films. The obtained structures were analyzed by tunneling microscopy. The Auger excitation process (Knotek–Feibelman mechanism) necessary for electron-stimulated oxygen desorption allows generation of ultrasmall structures. The subsequent processing step combines thermal desorption of the remaining monoxide and simultaneous etching promoted by thermally activated silicon atoms, which turns out to be a strongly anisotropic process close to step edges. Applying this combination of processes to a regularly stepped Si(557) sample, linewidths close to the resolution of the electron microscope of 5 nm were obtained.

In this study, carried out by analysis of intensities and spot profiles in low energy electron diffraction, we investigated the influence of electronegative oxygen atoms as dopants on the long range order, the thermal stability, and the type of phase transitions in the strongly anisotropic chain system Sr on Mo(112) in the low coverage regime at constant Sr concentrations up to 0.2 monolayers (ML), where the pure Sr layers show p͑8 ϫ 1͒ and p͑5 ϫ 1͒ structures, respectively. A single oxygen atom always influences many unit cells of Sr, as expected from a model of coupling the Sr chains by Friedel oscillations. Whereas concentrations of only 0.02 ML of oxygen transform the p͑8 ϫ 1͒ into a p͑9 ϫ 1͒ structure, small concentrations of oxygen atoms stabilize, but do not alter the p͑9 ϫ 1͒ structure over a wide range of oxygen concentrations. Oxygen induced disappearance of depinning transitions was found already for concentrations above 0.01 ML. For these concentrations only melting transitions are still observed. In a concentration range of oxygen and Sr atoms between 1:2 and 1:1 incommensurate structures are formed yielding finally islands of a ͑3.3ϫ 1͒ structure in all cases, interpreted as a sign of beginning formation of mixed oxides. Implications for adsorbate induced structuring of templates are discussed.