A key element of functionalizing nanocrystals with organic molecules is the nontemplated selective adsorption of different molecules on different facets. Here we report scanning-tunneling-microscopy images of perylene-3,4,9,10-tetracarboxylic-dianhydride and 2,5-dimethyl-N,N'-dicyanoquinonediimine on silver, demonstrating selective adsorption on different facets. We also report first-principles calculations that account for the data and show that bonding, which controls selectivity, occurs via the end atoms, while the molecule's midregion arches away from the substrate. The results are also consistent with data that have been interpreted in terms of bonding via the midregion.

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Single crystal diamond tips for scanning probe microscopy Rev. Sci. Instrum. 81, 013703 (2010); 10.1063/1.3280182 Scanning probe microscopy investigation of nanostructured surfaces induced by swift heavy ionsIon etching under well-defined conditions represents a very powerful tool to fabricate tips in a controlled and reproducible manner for Scanning Probe Microscopy which possess clean, relatively smooth, and oxide-free surfaces. The possibilities and limitations of ion etching are demonstrated thoroughly for tungsten, which is of particular interest for scanning tunneling microscopy. Iterative computer simulations and experimental studies are provided. The simulation of the etching process at the atomic level is based on the Monte Carlo program ͑Transport of Ions in Matter͒, which provides reliable values for the key input parameters such as the sputtering yield Y (,E ion ) and the mean ion range in the material for ion energies between 1 and 6 keV. The simulation program starts with a large tip radius as a crude form and asymptotically approaches a ''final form'' of a very sharp tip in the course of ion etching. Our experimental results with argon ions in the energy range up to 6 keV and crude electrochemically etched polycrystalline tungsten wire agreed very reasonably with the simulated results. For example, the minimum tip radius obtained experimentally amounts to approximately 5 nm. This value corresponds closely to the ion range, which obviously sets a limit to the smallest achievable tip radius by the effect of transmission sputtering. By variation of the angle between the ion beam and the macroscopic tip, the tip angle can be controlled in the range between 12°and 35°.

The radio channel assignment problem (CAP) is classified as an NP‐complete binary optimization problem, which creates the need for faster, yet optimal optimization algorithms to reduce the time of computation when solving such a complex problem. Simulated annealing (SA), a powerful optimal combinatorial search algorithm, was found to be very suitable for CAP. This paper extends the standard capabilities of SA and proposes a new CAP‐oriented, quicker binary SA, the binary dynamic SA (BDSA) algorithm, as part of a newly proposed radio channel assignment approach. Simulation results proved that the proposed BDSA has very fast convergence as a stand‐alone algorithm and even faster convergence with the newly proposed radio channel assignment approach. © 1998 John Wiley & Sons, Ltd.

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