We describe a technique for the fabrication of lateral nanometer-scale devices, in which individual metallic nanoparticles are imaged, selected and manipulated into a gap between two electrical leads with the tip of an atomic force microscope. In situ, real-time monitoring of the device characteristics is used to control the positions of the particles down to atomic accuracy and to tune the electrical properties of the device during fabrication. Using this technique we demonstrate a nanomechanical switch as well as atomic-scale contacts that are stable at quantized conductance levels on the time scale of hours at room temperature.

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We have fabricated gold single-electron transistors (SETs), operating up to 25 K, with tunnel gaps that could be individually tuned during fabrication. A combination of atomic-force-microscopy manipulation of nanodiscs and in situ electrical measurements was used to form statically stable tunnel gaps between the discs and lithographically defined electrodes. The gap resistances could be tuned to predetermined values over three orders of magnitude between ∼1 MΩ and ∼2 GΩ, corresponding to gap widths in the range of 3–10 Å. We report on SETs with symmetrically and asymmetrically coupled islands, i.e., with equal or different tunnel resistances. In the asymmetric SET a distinct Coulomb staircase was observed.

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