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One-dimensional diffusion of Co adatoms on graphene nanoribbons has been induced and investigated by means of scanning tunnelling microscopy (STM). To this end, the nanoribbons and the Co adatoms have been imaged before and after injecting current pulses into the nanoribbons, with the STM tip in direct contact with the ribbon. We observe current-induced motion of the Co atoms along the nanoribbons, which is approximately described by a distribution expected for a thermally activated one-dimensional random walk. This indicates that the nanoribbons reach temperatures far beyond 100 K, which is well above the temperature of the underlying Au substrate. This model system can be developed further for the study of electromigration at the single-atom level.

Different bridging geometriescan explain the observation that porphyrin molecules with added thiol end groups and pyridine axial groups form more‐stable single‐molecule junctions with an increased spread in low‐bias conductance. The stability of these geometries is demonstrated by time‐dependent conductance measurements. In contrast, rodlike molecules show one preferential binding geometry.

Unterschiedliche Brückengeometrienkönnen die Beobachtung erklären, dass Porphyrinmoleküle mit Thiolendgruppen und axialen Pyridingruppen stabilere Einzelmolekülkontakte mit einer größeren Spanne der Ruheleitfähigkeit bilden. Die Stabilität dieser Geometrien wurde in zeitabhängigen Leitfähigkeitsmessungen gezeigt. Stäbchenförmige Moleküle dagegen haben eine bevorzugte Bindungsgeometrie.

Electrochemical methods have recently become an interesting tool for fabricating and characterizing nanostructures at room temperature. Simplicity, low cost and reversibility are some of the advantages of this technique that allows to work at the nanoscale without requiring sophisticated instrumentation. In our experimental setup, we measure the conductance across a nanocontact fabricated either by dissolving a macroscopic gold wire or by depositing gold in between two separated gold electrodes. We have achieved a high level of control on the electrochemical fabrication of atomic-sized contacts in gold. The use of electrochemistry as a reproducible technique to prepare nanocontacts will open several possibilities that are not feasible with other methodologies. It involves, also, the possibility of reproducing experiments that today are made by more expensive, complicated or irreversible methods. As example, we show here a comparison of the results when looking for shell effects in gold nanocontacts with those obtained by other techniques. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The present special issue of physica status solidi (a) contains contributions from the TNT2006 – Trends in Nanotechnology Conference, held in Grenoble, France, 4–8 September 2006.Editor's Choice is the article by Reyes Calvo et al. [1], which reports on the possibilities of using electrochemical methods to form atomic-sized contacts. In particular, the authors analyze previous attempts and propose improvements on several methods, in order to increase the control and the ease of preparation of the nanocontacts. The cover picture shows the electrochemical cell (1 cm in diameter) used for the experiments (left) with a schematic of the electronic circuit used. An artistic view of the atomic contact is depicted at the top. The lower right panel shows the last stages of the evolution of the conductance of a gold wire while being electrochemically etched. The last plateau of conductance corresponds to a one-atom contact. The upper right panel shows the voltamogram of the wire prior to etching.This work was done mainly at the Low Temperatures & Nanotechnology Laboratory of the University of Alicante (Spain), lead by Dr. Carlos Untiedt. He is a “Ramon y Cajal” Researcher whose main research interest is the electronic transport in nanostructures, and in particular in atomic-sized contacts.The issue also contains an Original Paper on scientific policy entitled “Nanotechnology applications: a driving force for R&D investment” [2], and a Feature Article presenting a report on the synthesis of luminescent silicon nanostructures by means of laser ablation techniques by Riabinia et al. [3]. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)