Three letters beamed across a lab bench may spark a revolution in wireless communication. The seemingly simple transmission of “IBM” was received by the first working radio chip to be made from the modern wonder material, graphene – sheets of carbon, each just one atom thick.

Graphene, with its flat, hexagonal lattice, was first isolated a decade ago. It won its discoverers a Nobel prize in physics, in part because its high electrical and thermal conductivity led to broad predictions that it would completely replace silicon transistors, the key component in many electronics. This latest achievement shows that analogue circuits such as radios can indeed make use of the material, potentially leading to cheaper, more efficient wireless devices.

Until now, making wireless circuits like the ones in Bluetooth and WiFi chips has not been possible with graphene transistors, because it is too delicate a material and only weakly adheres to the standard silicon base. In 2011, IBM researchers made a radio microchip with graphene transistors, but they found that placing other necessary metal components, such as resistors and coils, on top of the transistors physically damaged them. This seriously degraded their ability to amplify voltages – a key requirement when attempting to boost feeble radio signals – and the team was not able to receive a broadcast.

“Taming this new material so we could process it properly, and without damaging it, became our biggest challenge,” says Supratik Guha, IBM’s director of physical sciences at the company’s lab in Yorktown Heights, New York. With funding from the US Pentagon’s Defence Advanced Research Projects Agency (DARPA), a team led by IBM’s Shu-Jen Han has found the answer: make graphene-based chips in reverse.


Reverse the flow

The team found that if they place the metal components on the chip first and then add the graphene transistors, the devices do not suffer the same structural stresses and damage as the 2011 chip. “We found that simply by reversing the flow of the manufacturing process, the gain of graphene transistors is now 10,000 times better than before,” says Han. The team built the chips on standard silicon wafers, suggesting no major changes in production technology will be necessary.

To test the circuit, the team sent a radio signal containing the letters I, B and M, and the device received it perfectly, its makers claim. Graphene’s high conductivity means the graphene circuit uses less power than traditional radio chips, which makes it attractive for use in the wearable radio devices DARPA wants for the US military.

Feverish research competition in the graphene arena meant a spokesman for a rival lab preferred to comment anonymously on IBM’s work. The result is impressive, he says. He still thinks it will be at least 20 years before graphene chips become commonplace, and even then devices like IBM’s, which mix graphene and silicon, will have the best shot at success.

Journal reference: Nature Communications, DOI: 10.1038/ncomms4086