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Friction force measurements performed by means of an atomic force microscope (AFM) under electrochemical conditions on a pure Au(111) electrode surface and one modified with a foreign metal are presented; after deposition of a (sub)monolayer copper on a Au(111) single crystal electrode a large increase of the friction force is observed compared to the pure Au(111) electrode surface; the extent of the increase not only depends on the copper coverage, but also on the normal load and may be explained by a higher energy dissipation due to motion of the sulfate anions adsorbed on the copper atoms induced by the AFM tip.

KEYWORDS:alloys ¥ gold electrode ¥ quantum point contact ¥ scanning probe microscopy ¥ tunneling resistance A new way of nanostructuring a gold electrode surface with the STM tip will be described. Due to a force interaction between the STM tip and the substrate surface, covered by a UPD monolayer (UPD underpotential deposition) of Cu or Pd atoms, a local alloy is formed. By measuring the conductance G, which characterizes the minimal distance of the STM tip to the surface, necessary for generating the nanostructures, we get an insight into the possible mechanism. The conductance is in the range as expected from quantummechanics for a point contact. Due to this result we assume that a point contact between the STM tip and the UPD-covered surface is formed.The preparation of structures with lateral dimensions on the nanometer-scale attracts an increasing interest, since it has been shown that the physical and chemical properties of such nanostructures can strongly deviate from the properties of the corresponding bulk materials. In recent years, the electrochemical scanning tunnelling microscope (EC-STM) has often been used as a tool to modify electrode surfaces on a nanoscopic scale. Kolb et al. have demonstrated that very small metal clusters can be generated with the EC-STM by a special technique of a tip induced metal deposition, the so called ™jump-to-contact∫ method.[1] This technique involves electrolytic deposition of the metal (for example a Cu metal) onto the STM tip, followed by a controlled approach during which metal is transferred from the tip to the surface (for example a Au metal). It was shown that the metal to be deposited (Cu, Pb, Ag, Pd) as well as the substrate metal (Au, Ag) can be varied.

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