A small bit of carbon could make radio communications components at the heart of mobile phones smaller and less expensive.
That is all thanks to graphene. IBM is able to pull useful wireless-communications work out of graphene, a form of carbon whose promise in next-generation computer chips suffered because manufacturing difficulties.
IBM did say, however, 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, does have properties useful for replacing today’s silicon for electronics transistors. But graphene’s fragility means 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 integrate with other computing functions.
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.”
The data rate with the test chip was 20 megabits per second, IBM said — but the test equipment limited the test, 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,” said researchers Shu-Jen Han, Alberto Valdes Garcia, Satoshi Oida, Keith A. Jenkins, and Wilfried Haensch in a research paper on the subject.
The graphene-based receiver ended up built onto a chip with an area of 0.6 square millimeters, IBM said.