Graphene nanoribbons show metallic properties

Researchers from Aalto University in Finland have developed graphene nanoribbons (GNRs) that exhibit metallic properties and could be used in future electronic devices.

GNRs have been suggested as ideal materials for nanoelectronics, where wiring is reduced to the atomic scale. The GNRs created by the team at Aalto, described in the journal Nature Communications Science, are just five carbon atoms wide and one atom thick. Unlike other GNRs, they are not semiconducting, which means they could potentially be used as metallic interconnects in future microprocessors.

Graphene nanoribbons (Credit: Aalto University)
Graphene nanoribbons (Credit: Aalto University)

The GNRs are fabricated through a chemical reaction that takes place on a substrate. According to Dr Pekka Joensuu, who oversaw the synthesis of the precursor molecules for the ribbons, different surface molecules can dictate the width of the graphene.

“The cool thing about the fabrication procedure is that the precursor molecule exactly determines the width of the ribbon,” he said. “If you want one-carbon-atom-wide ribbons, you simply have to pick a different molecule.”

Once the ribbons were created, the team used a technique called scanning tunnelling microscopy (STM), which allowed them to view the material’s structure and properties with atomic resolution.

“With this technique, we measured the properties of individual ribbons and showed that ribbons longer than 5 nanometers exhibit metallic behaviour,” said Dr Amina Kimouche, the lead author of the study.

The ultra-narrow ribbons have major potential in the field of nanoelectronics, where it is suggested they could replace copper as the interconnect material. Future studies carried out at Aalto University will focus on all-graphene devices that combine both metallic and semiconducting graphene nanostructures. However, commercial applications are still some way off yet according to Prof Peter Liljeroth, who headed up the research.

“While we are far from real applications, it is an extremely exciting concept to build useful devices from these tiny structures and to achieve graphene circuits with controlled junctions between GNRs,” he said.