25 July 2017

Publication in Nature Communications

Chemical pathway produces graphene electronic circuits with atomic precision

Metaal-halfgeleider-metaalovergang in een enkel grafeen nanolint
Metal-semiconductor-metal junction (tunnel barrier) incorporated into a single graphene nanoribbon

Essential electronic components, such as diodes and tunnel barriers, can be incorporated in single graphene wires (nanoribbons) with atomic precision. The result is a working electronic device that could be used in graphene-based electronic switches with extremely fast operational speeds. Chemists at Utrecht University made this discovery together with their colleagues at TU Delft and the Aalto University in Finland. The work is published in Nature Communications on 25 July.

The ‘wonder material’ graphene has many interesting characteristics, and researchers around the world are hard at work looking for new ways to utilise them. Graphene itself does not have the characteristics needed to switch electrical currents on and off, however, so smart solutions must be found for that particular problem. “The great thing about our solution is its atomic precision. By selecting certain precursor substances (molecules), we can code the structure of the electrical circuit with extreme accuracy”, explains research leader Ingmar Swart from Utrecht University.

Seamless integration

The switch is based on the principle of graphene nanoribbons. Previous research has shown that the ribbon’s electronic characteristics are dependent on its atomic width. A ribbon that is five atoms wide is an ordinary electric wire with extremely good conduction characteristics, but adding two atoms makes the ribbon a semiconductor. “We are now able to seamlessly integrate a five-atom wide ribbon together with one that is seven atoms wide. That gives you a metal-semiconductor junction, which works as a diode”, according to Swart.

De chemische route naar een elektronische schakeling in grafeen
The chemical pathway to graphene electronic circuits

Chemistry on a surface

The researchers produced their electronic graphene structures through a chemical reaction. They evaporated the precursor molecules onto a gold crystal, which created new chemical compounds. “This is a different method from that currently used to produce electrical nanostructures, such as those on computer chips. For graphene, it is so important that the structure is precise at the atomic level, and it is likely that the chemical route is the only effective method”, Swart adds.        

Electronic characteristics

The researchers also determined the electronic and transport characteristics of the resulting structures. They created and tested a fully functional electronic diode made from a single graphene nanoribbon. The characteristics of this structure corresponded to the theoretical expectations of the structure.   

This research was funded in part by the NWO Graduate Programme, the Academy of Finland and the European Research Council.

Publication

‘Electronic components embedded in a single graphene nanoribbon’
P. H. Jacobse*, A. Kimouche**, T. Gebraad***, M. M. Ervasti**, J. M. Thijssen***, P. Liljeroth**, I. Swart* (*Utrecht University, **Aalto University School of Science, ***Delft University of Technology)
DOI: 10.1038/s41467-017-00195-2

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