Breakthrough carbon ring could have outsized impact on molecular electronics

Carbon may be commonplace in the grand scheme of elements in our universe, but some of its forms are much rarer than others – something IBM Research took as a challenge that could shake up future electronics. A team there, in collaboration with the University of Oxford, has created a so-called cyclocarbon ring for the first time.

Carbon atoms typically bond with three or four of their neighbors, at least in the most common forms we encounter. In graphite, for example, each carbon atom links with three other carbon atoms. In diamonds, the carbon atoms link with four others.

Cyclocarbons, however, cut those pairings down to two. In that way, they make a ring structure. While they've been theoretically understood for years now, because of their high level of reactivity – their tendency to link with another atom and break up the ring – they've proved impossible to isolate.

Three years ago, researchers set out to try to change that. They used an inert surface on which to grow a cyclocarbon ring at very low temperatures, then used atomic force microscopy (AFM) to image it. Even then, however, it was hardly an easy process.

The IBM Research and University of Oxford team started out with a layer of table salt, which is relatively inert, atop a copper substrate. Because of that reluctance to react, the sale wouldn't form covalent bonds with carbon atoms laid on top. First, the team made linear segments, and then built a ring made up of eighteen carbon atoms stabilized with six carbon monoxide groups.

After that, it was a matter of carefully removing the carbon monoxide and hoping that the carbon atoms would stay linked even without their scaffold. By applying voltage pulses to the tip of an AFM, the carbon monoxide groups could be removed in pairs.

As long as the surface of the substrate was kept cold – 5 Kelvin, or around -450 degrees Fahrenheit – the cyclocarbon ring proved stable enough to investigate. It allowed researchers to settle one of the lingering questions about the formation: whether the ring would be formed entirely by double bonds, or by alternating single and triple bonds. Turns out, the latter is true.

It's not just theory that's being settled, however. By demonstrating. That atom manipulation can fuse cyclocarbons and cyclic carbon oxides, the researchers suggest that a whole host of carbon-rich molecules and other forms could be created in the future.

That potentially paves the way to molecular electronics, where molecules are used to create electronic components but at vastly smaller scales than traditional silicon circuits. In that way, new computers that break out of Moore's Law using nanotechnology to individually craft electronics might one day be not only feasible, but practical.