Pushing the limits of silicon electronics to make smaller, faster and more efficient devices is getting harder. One possible way forward is to take advantage of the many phenomenal properties of nanocarbon structures that have been discovered over the past 40 years. However, amongst this suite of carbon nanomaterials there has been a conspicuous lack of wire-like materials with metallic properties that can be reliably customized and produced. This poses a challenge because connecting nanocarbon semiconductor components with the same old copper or silver wires can take the shine off their appeal.
While carbon nanotubes with metallic properties can be made with relative ease, the snag is that a heap of nanotubes with semiconducting properties are inevitably produced at the same time. Unfortunately, separating metallic nanotubes from semiconductor nanotubes en masse remains something of a dark art. Another option is graphene; with the unprecedented mobility of its π-electrons, doping can push graphene’s conductivity well above copper. But if graphene is cut into strips called graphene nanoribbons (GNRs) to make wires for interconnects, the material’s delocalized electrons become confined by the width of the nanoribbon. This opens a bandgap that makes the material a semiconductor or even an insulator.
Now, researchers in the US have shown how to produce graphene nanoribbons with robust metallic properties to order, providing the missing link for all-carbon electronic devices. The work was led by Daniel Rizzo, Gregory Veber and Jingwei Jiang, who are researchers in the labs of Michael Crommie, Felix Fischer and Steven Louie at the University of California, Berkeley.
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