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Graphene vs. nanotubes
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International Business Machines Corp., of Yorktown Heights, NY received a cost type contract for $2.4 million, under the “Wafer-Scale Graphene RF Nanoelectronics effort.” This effort is connected to DARPA’s CERA effort. The project’s goal is to investigate 2 challenges that are fundamental to development of high performance carbon electronics for military radio frequency applications in military systems. The Air Force Research Laboratory at Wright-Patterson Air Force Base, OH manages the contracts (FA8650-08-C-7838). At this time all funds have been obligated.

IBM fellow Phaedon Avouris, the manager of Nanoscale Science at the Research Center, explains:

“Unlike silicon, which has a bandgap that you bridge to have electrical transport, graphene does not have a gap, so you can’t ordinarily turn it on and off like a transistor. But we have discovered how to open up a gap by confining the electrons in a very narrow ribbon of material, in a manner similar to a nanotube, producing a quantum wire…. Nanotubes and graphene are essentially the same thing, but nanotubes have nice well-defined edges, whereas it is very difficult to cut graphene into well defined ribbons…. But by using unconventional cutting techniques, we hope to narrow the nanoribbons [from 20 nanometers] to about two nanometers, which we think will result in a room-temperature graphene FET.”

Why does this matter? Partly because graphene is one of the non-silicon options for future electronics that offers researchers the possibility of good performance with much less power draw. In that sense, these kind of non-silicon options represent the next step after DARPA programs like STEEP. Graphene also has advantages of placement and uniformity over carbon nanotubes, because it’s a planar sheet rather than a tube.

The first applications of the nanoribbon FETs will be for RF devices, which can include both radio and radar-related applications. The high electron mobility of graphene makes it an excellent candidate for analog ultra-high-frequency oscillators and switches.

Additional Readings

• DARPA – Carbon Electronics for RF Applications (CERA)

• 2007 Microsystems Technology Symposium in San Jose, CA – Future of Power Efficient Processing by Dr. Michael Fritze, DARPA MTO [PDF]

• RF Globalnet (May 28/08) – Researchers Develop Method To Create Transistors Out Of Carbon Nanoribbons

• IEEE Times (Oct 1/07) – IBM fabs grahene FETs. Includes Avouris quote.

• DID (Feb 13/08) – $6.4M to IBM to Research Non-Thermionic Transistors. Under a program called STEEP, which also aims to produce very low power transistors using techniques one step less revolutionary than non-silicon options like graphene.