The smoothing kinetics of Ag(110) studied by thermal energy He atom scattering

The smoothening process of nanometer-scale ripples grown on the (110) surface of silver is investigated using thermal energy He atom scattering. Morphological equilibration the corrugated surface is followed in real time in the temperature range between 205 and 230 K. The mean ripple wavelength, Lambda, is observed to increase during surface recovery. To take this effect into account the decay time is assumed to scale as Lambda(3). Within this approximation the ripple amplitude is observed to decay linearly with time. The activation energy of the mechanism driving surface relaxation is estimated as (0.46 +/- 0.02) eV. The underlying rate limiting process, i.e. adatom detachment from the open <001> step edges is evidenced. (C) 2004 Elsevier B.V. All rights reserved

Friction reduction of Ne monolayers on preplated metal surfaces

With a quartz-crystal microbalance technique we have studied the nanofriction of Ne monolayers at temperatures below 6.5 K and in ultrahigh-vacuum conditions deposited on metallic surfaces plated with heavy rare-gases multilayers. Covering the electrode with one layer of Kr or Xe increases the slippage of a Ne monolayer by a factor close to 3. Such a behavior has been observed with smooth lead electrodes as well as with rougher gold ones. The lubrication effect does not improve with thicker overlayers

Low-temperature static friction of N-2 monolayers on Pb(111)

Using a quartz crystal microbalance technique, we have measured the interfacial viscosity of nitrogen monolayers deposited on very homogeneous Pb(111) surfaces. At temperatures below 15 K, no dissipation is detected, suggesting that the N-2 films are rigidly coupled to the oscillating electrode. By raising the temperature close to 20 K, we find sliding of the nitrogen film for coverages above about 0.5 nominal layers. The observed temperature dependence is in good qualitative agreement with recent calculations on the static friction of a nitrogen slab in contact with a crystalline Pb substrate

Structural depinning of ne monolayers on Pb at T < 6.5 k

We have studied the nanofriction of Ne monolayers with a quartz-crystal microbalance technique at temperatures below 6.5 K and in ultrahigh-vacuum conditions. Very homogeneous and smooth lead electrodes have been physically deposited on a quartz blank at 150 K and then annealed at room temperatures. With such a Pb-plated quartz-crystal microbalance, we have observed a pronounced depinning transition separating a low-coverage region, where the film is nearly locked to the oscillating electrode, from a high-coverage region characterized by slippage at the solid-fluid boundary. Such a behavior has been found to be very reproducible. These data are suggestive of a structural depinning of the solid Ne film when it becomes incommensurate with the lead substrate, in agreement with the results of an extensive molecular-dynamics study

In-situ study of the dewetting behavior of Ni-films on oxidized Si(001) by GISAXS

none10R.FELICI; N.M. JEUTTER; V. MUSSI; F. BUATIER DE MONGEOT; C. BORAGNO; U.VALBUSA; A.TOMA; Y.WEI; C. RAU; I.K. ROBINSONR., Felici; N. M., Jeutter; Mussi, Valentina; BUATIER DE MONGEOT, Francesco; Boragno, Corrado; Valbusa, Ugo; Toma, Andrea; Y., Wei; C., Rau; I. K., Robinso

Re-radiation Enhancement in Polarized Surface-Enhanced Resonant Raman Scattering of Randomly Oriented Molecules on Self-Organized Gold Nanowires

We explore the effect of re-radiation in surface-enhanced Raman scattering (SERS) through polarization-sensitive experiments on self-organized gold nanowires on which randomly oriented Methylene Blue molecules are adsorbed. We provide the exact laws ruling the polarized, unpolarized, and parallel- and cross-polarized SERS Intensity as a function of the field polarizations. We show that SERS is polarized along the wire-to-wire nanocavity axis, independently from the excitation polarization. This proves the selective enhancement of the Raman dipole component parallel to the nanocavity at the single molecule level. Introducing a field enhancement tensor to account for the anisotropic polarization response of the nanowires, we work out a model that correctly predicts the experimental results for any excitation/detection polarization and goes beyond the E(4) approximation. We also show how polarization-sensitive SERS experiments permit one to evaluate independently the excitation and the re-radiation enhancement factors accessing the orientation-averaged non-diagonal components of the molecular Raman polarizability tensor