The Kondo resonance of Co adatoms on the Cu(100) and Cu(111) surfaces has been studied by scanning tunneling spectroscopy. We demonstrate the scaling of the Kondo temperature T(K) with the host electron density at the magnetic impurity. The quantitative analysis of the tunneling spectra reveals that the Kondo resonance is dominated by the Cu bulk electrons. While at the Cu(100) surface both tunneling into the hybridized localized state and into the substrate conduction band contribute to the Kondo resonance, the latter channel is found to be dominant for Cu(111).

We report on long-range interactions between adsorbates on metal surfaces with a surface state. A comparison of three adsorbate/substrate systems ͓Cu/Cu͑111͒, Co/Cu͑111͒, and Co/Ag͑111͔͒ suggests the general existence of such interactions and shows up common characteristics. In all cases, the interaction energy E(r) manifests itself up to a distance of 60 Å, decays as 1/r 2 , and oscillates with a period of F /2. Our data are in excellent agreement with theory and establish the link between the spatial variation of the interaction energy and the adsorbate scattering properties. We demonstrate that the long-range interactions stabilize an ordered two-dimensional ͑2D͒ gas of adsorbates and thus create states of dilute 2D matter. At larger separations adsorbate interactions are predominantly indirect and may be mediated in three ways: electrostatically ͑dipole-dipole͒ and elastically ͑deformation of substrate lattice͒, which both lead to nonoscillatory interactions that decay monotonically with separation r as 1/r 3 . 3 The third way of mediation, which is the subject of the present study, is by substrate electrons leading to an oscillatory interaction energy.A foreign atom dissolved in a solid, or adsorbed on a surface, imposes its potential onto the host electrons, which they screen by density oscillations. Friedel introduced such oscillations with wave vector 2k F to calculate the conductivity of dilute metallic alloys. 4 Whereas Friedel oscillations in the bulk escape from direct observation, they become apparent at the surface.5 Scanning tunneling microscopy ͑STM͒ images taken at low bias directly reflect the oscillating quantity, namely, the local density of states close to E F , enabling a direct observation of Friedel oscillations. The first case was reported for carbon atoms adsorbed on Al͑111͒. 6 The original data are reproduced in Figs. 1͑a͒ and 1͑b͒ for contrasting Friedel oscillations of bulk electrons with those of surfacestate electrons ͓Figs. 1͑c͒ and 1͑d͔͒. In Fig. 1͑a͒ two C atoms appear as localized protrusions. In Fig. 1͑b͒ the same area is scanned at smaller tip-sample distance, which has the effect that the C atoms become transparent. This reveals the redistribution of substrate electrons particularly clearly. Carbon withdraws charge from the three nearest Al neighbors, which, therefore, appear darker (⌬zϭϪ0.34 Å). Due to Friedel oscillations, the next-nearest Al neighbors accumulate charge and appear brighter (⌬zϭϩ0.18 Å).Inspecting Figs. 1͑a͒ and 1͑b͒ one realizes that adsorbates may interact via Friedel oscillations through the fact that the binding energy of one adsorbate depends on the substrate electron density, which oscillates around the other adsorbate. Lau and Kohn predicted such oscillatory interactions to depend on distance as cos(2k F r)/r 5 . 7 Hence the bulk, threedimensional ͑3D͒, electron mediated adsorbate interactions fall off much faster than the dipole-dipole and elastic interactions. The superposition of all three indirect interactions, dipole-dipole, elastic, and bulk-el...

The hysteresis and kinetics of capillary condensation of N2 and Ar in linear mesopores, produced by etching of Si wafers, have been studied for different pore shapes, including the ink bottle geometry. Pore blocking has been observed in the solid state of the pore fillings, but not in the liquid state. We conclude that individual local geometries such as the pore mouth, a blind end, or a single constriction have no effect on the shape of sorption isotherms, that the pore space should be regarded as a statistical ensemble of pore segments with a lot of quenched disorder.

Tethered membranes have been proven during recent years to be a powerful and flexible biomimetic platform. We reported in a previous article on the design of a new architecture based on the self-assembly of a thiolipid on ultrasmooth gold substrates, which shows extremely good electrical sealing properties as well as functionality of a bilayer membrane. Here, we describe the synthesis of lipids for a more modular design and the adaptation of the linker part to silane chemistry. We were able to form a functional tethered bilayer lipid membrane with good electrical sealing properties covering a silicon oxide surface. We demonstrate the functional incorporation of the ion carrier valinomycin and of the ion channel gramicidin.