Jun 14, 2013
Graphene makes first digital GHz oscillator
Researchers in the US and Italy have succeeded in making the first integrated graphene digital circuits that function at gigahertz (GHz) frequencies. The circuits in question are ring oscillators and the work is an important step towards realizing all-graphene microwave circuits, says the team.
Graphene (a 2D sheet of carbon just one atom thick) and other novel 2D materials (like carbon nanotubes and molybdenite) show great promise for future electronics because they could allow devices smaller than 10 nm to be made. 10 nm is around the dimension at which devices based on conventional silicon reach their limits. Until now, however, no one had succeeded in making high-frequency digital circuits from these materials. Indeed, the best carbon nanotube ring oscillator made to date operates at just 50 MHz.
A team led by Roman Sordan of the Politecnico di Milano and Eric Pop of the University of Illinois now reports on the first integrated graphene oscillators ever, and the first high-frequency digital circuits based on any type of novel low-dimensional material. The graphene ring oscillators, which operate at 1.28 GHz to be precise, also appear to be less sensitive to fluctuations in the supply voltage compared to both conventional silicon CMOS and oscillators made from the 2D materials mentioned earlier.
Final 'missing' component
Oscillators are also one of the main building blocks of analogue electronics – for example, radio-frequency (microwave) electronics are based on voltage amplifiers, oscillators and mixers. "Graphene amplifiers and mixers have already been demonstrated so the oscillators we made represent the final 'missing' component for making all-graphene microwave circuits," Sordan told nanotechweb.org.
And that is not all: the team has also managed to fabricate stand-alone graphene frequency mixers from its ring oscillators. All previously demonstrated graphene mixers were not stand-alone because they required external oscillators to function, but this is not the case for ours, explains Sordan.
"We believe that our study significantly advances research in low-dimensional nanomaterials towards practical, high-speed digital and analogue applications, and we hope that it will motivate significant future work in this direction," he adds.
The research is reported in ACS Nano.
About the author
Belle Dumé is contributing editor at nanotechweb.org.