Good connections to molecular electronics: how molecular wires can be optimised

The electronics of the future could use molecules to do their arithmetic. The tiny particles could then take over the tasks which are presently done by silicon transistors, for example.

Researchers from the Fritz Haber Institute of the Max Planck Society in Berlin have used a nanowire which could potentially conduct current between molecular transistors or different components.

The tiny conducting track consists of a narrow graphene band, that is a strip of a single layer of carbon. Their next step was to use a scanning tunnelling microscope to perform complicated measurements to determine how the conductance of the carbon strip depends on its length and the energy of the electrons.

They thus learned more about how charge in the form of electrons is transported through the nanowire and how the conducting tracks can be improved for potential applications in nanoelectronics.

A wire can hardly be any thinner. But the record-breaking dimensions of graphene wires not only offer new opportunities, they also confront physicists with challenges. Leonhard Grill and his colleagues at the Berlin Fritz Haber Institute of the Max Planck Society have now taken on these challenges. They began by producing a narrow graphene ribbon, its design based on their own work and that of others. Firstly, they vaporised molecular snippets of graphene strips onto a surface. The molecules were provided with chemical bonds so that they initially combined into a long chain and finally formed a flat, rigid ribbon.

A delicate touch is needed to measure the conductance of nanowires
Then the researchers in Leonhard Grill's group started their real project: they measured the conductance of one individual nanowire as a function of its length. ''This enables us to find out how the charge transport in the graphene nanowire works,'' explains Leonhard Grill. This approach primarily allows the researchers to find out whether their nanowire is a perfect conductor whose conductance does not vary with length, as would be the case with a metal nanowire.