Nanostructured, glassy carbon ͑GC͒ supported Pt/GC electrodes, with Pt nanostructures ͑nanodisks͒ of controlled size ͑100-140 nm in diameter͒ and separation homogeneously distributed on a planar GC substrate, were recently shown to be interesting model systems for electrocatalytic reaction studies ͓M. Gustavsson, H. Fredriksson, B. Kasemo, Z. Jusys, C. Jun, and R. J. Behm, J. Electroanal. Chem., 568, 371 ͑2004͔͒. We present here electron microscopy and electrochemical measurements which reveal that the fabrication of these nanostructured electrodes via colloidal lithography, in addition to the intended nanodisks, results in a dilute layer of much smaller Pt nanoparticles ͑diameter ϳ5 nm͒ on the GC surface in the areas between the Pt nanodisks. We further demonstrate that by using the developed, related method of hole-mask colloidal lithography ͑HCL͒ ͓H. Fredriksson, Y. Alaverdyan, A. Dmitriev, C. Langhammer, D. S. Sutherland, M. Zäch, and B. Kasemo, Adv. Mater. (Weinheim, Ger.), 19, 4297 ͑2007͔͒, similar electrodes can be prepared which are free from these Pt nanoparticles. The effect of the additional small Pt nanoparticles on the electrochemical and electrocatalytic properties of these nanostructured electrodes, which is significant and can become dominant at low densities of the Pt nanodisks, is illustrated and discussed. These results leave HCL the preferred method for the fabrication of nanostructured Pt/GC electrodes, in particular, of low-density Pt/GC electrodes.

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We demonstrate the controlled and reproducible structuring of surfaces of muscovite mica with the tip of an atomic force microscope operated in contact mode under ambient conditions. By repeated scanning of the tip along a predefined pattern on a cleaved mica surface at forces between 100 nN and 4 µN, mechanically induced etching was observed on the atomic scale. Using silicon nitride tips, no tip wear was observed during structuring. No debris was found on the surface as a result of the structuring process, indicating the atomic-scale nature of the wear process. Line widths down to 3 nm were achieved, while at the same time patterns on a wide range of length scales between 5 nm and 100 µm were generated reproducibly. The results can be explained by abrasive wear on the atomic scale due to sliding friction. The experiments allow the study of tribochemistry and abrasive wear on the atomic and molecular scale. At the same time, they represent an approach for high-precision structuring of surfaces within a wide range of length scales.

For the quantitative investigation of surface properties such as elasticity, friction and wear by atomic force microscopy (AFM), a quantitative determination of the forces acting on the probe during its motion along the sample surface is essential. In this article, a fully parameterized finite element model for V-shaped cantilevers is presented and the three-dimensional mechanical deformations of the AFM cantilever are investigated. Force constants and detection angles for tip displacements in the three spatial directions are calculated for widely used cantilevers. The limits of linearity according to Hook's law are studied. It is found that the AFM contact cantilevers investigated here show a linear bending behavior for tip displacements within a range below approx. 10 nm in lateral directions and 100 nm in the normal direction. Displacements within this range are typical for many AFM applications including force modulation techniques. For higher loads as used e.g. for surface modification, a significant deviation from linear behavior is observed.