Elhuyar Fundazioa

Manufacturing 'made to measure' atomic-scale electrodes

Thanks to collaborative work between scientists in Donostia-San Sebastian and the University of Kiel (Germany) it has been shown that it is possible to determine and control the number of atoms in contact between a molecule and a metal electrode of copper, at the same time as the electric current passing through the union being recorded. These results were published in the Nature Nanotechnology journal.

One of the key problems in nanotechnology is the formation of electrical contacts at an atomic scale. This demands the detailed characterisation of the current flowing through extremely small circuits – so small that their components can be individual atoms or molecules. It is precisely this miniature nature of the system, of typically nanometric dimensions (1 metro = a thousand million nanometers), where the difficulty of this yet unresolved problem arises. In particular, in unions formed by a single molecule, it has been shown that the number of individual atoms making up the contact and their positions are crucial when determining the electric current that is flowing. To date, there has been no experiment where it has been possible to control these parameters with sufficient precision.

In the research published by the Nature Nanotechnology journal, however, these scientists have revealed and explained the changes that the electric current flowing through a molecular union (metal/molecule/metal) undergoes, depending on the area of contact uniting the molecule to the metallic electrodes. Basically, changing the number of atoms in contact with the molecule, one by one, it goes from a low state (bad contact) to another, higher one (good contact) of conduction. With bad contact the current is limited by the area of contact, while with good contact the current is limited by the intrinsic properties of the molecule.