Researchers at Big Blue improved graphene-based radio receiver performance by attaching the fragile form of carbon material at the end of the chipmaking process.
A teensy bit of carbon could make the radio communications components at the heart of mobile phones smaller and less expensive.
IBM has coaxed useful wireless-communications work out of graphene, a form of carbon whose promise in next-generation computer chip has been hobbled by manufacturing difficulties. In an IBM Research paper published Thursday in Nature Communications, Big Blue describes how it has built a graphene-based receiver integrated circuit that successfully extracted the letters "IBM" from a 4.3GHz radio broadcast.
Graphene, which consists of a lattice of carbon atoms interconnected into a layer just a single atom thick, has shown properties useful for replacing today's silicon for electronics transistors. But graphene's fragility means that manufacturing processes that marry graphene with traditional silicon chip circuitry can damage the graphene and undermine its performance.
What IBM researchers figured out is a way to add the graphene after its underlying silicon chip is already built instead of constructing the chip around the graphene. The result is an integrated circuit that combines graphene field-effect transistors (GFET) with other components used in radio communications. The approach dovetails well with traditional silicon CMOS (complementary metal oxide semiconductor) technology for manufacturing chips, making it more likely that the radio-frequency technology can be integrated with other computing functions.
And it works.
IBM successfully used the graphene-based receiver to process a digital transmission on a 4.3GHz radio frequency. The digits transmitted were "01001001," "01000010," and "01001101" -- a binary encoding of the letters "IBM."
This photo shows a slice of silicon with an array of dozens of graphene-based receiver chips. The graphene was added during the final manufacturing stages, an approach that helped preserved the thin sheet of carbon atoms from harm.
(Credit: IBM)The data rate with the test chip was 20 megabits per second, IBM said -- but that was limited by the test equipment, not the graphene-based receiver itself.
"One can envision that high-performance graphene radio-frequency circuits will be directly built on top of high-density silicon CMOS logic circuits to form an extremely low-cost, ultra-compact communication system," wrote researchers Shu-Jen Han, Alberto Valdes Garcia, Satoshi Oida, Keith A. Jenkins, and Wilfried Haensch.
The graphene-based receiver was built onto a chip with an area of 0.6 square millimeters, IBM said.
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