by Playfuls Staff |
1st March 2007
Researchers have used the world's thinnest material to
create the world's smallest transistor – a breakthrough that could spark the
development of a new type of super-fast computer chip. [more]
Professor Andre Geim and Dr Kostya Novoselov from The School
of Physics and Astronomy at The University of Manchester, reveal details of
transistors that are only one atom thick and less than 50 atoms wide, in the
March issue of Nature Materials.
They believe this innovation will allow the rapid
miniaturisation of electronics to continue when the current silicon-based
technology runs out of steam.
In recent decades, manufacturers have crammed more and more
components onto integrated circuits. As a result, the number of transistors and
the power of these circuits has roughly doubled every two years. This has
become known as Moore's
Law.
But the speed of cramming is now noticeably decreasing, and
further miniaturisation of electronics is to experience its most fundamental
challenge in the next ten to 20 years, according to the semiconductor industry
roadmap.
Two years ago, Professor Andre Geim and his colleagues
discovered a new class of materials that can be viewed as individual atomic
planes pulled out of bulk crystals.
These one-atom-thick materials and particularly graphene – a
gauze of carbon atoms resembling a chicken wire – have rapidly become one of
the hottest topics in physics.
The first graphene-based transistor was reported by The
University of Manchester team at the same time as the discovery of graphene,
and other groups have recently reproduced the result.
But these graphene transistors were very 'leaky', which has
limited possible applications and ruled out important ones, such as their use
in computer chips and other electronic circuits with a high density of
transistors.
Now the Manchester
team has found an elegant way around the problem and made graphene-based
transistors suitable for use in future computer chips.
Professor Geim and colleagues have shown for the first time
that graphene remains highly stable and conductive even when it is cut into
strips of only a few nanometres wide. All
other known materials – including silicon – oxidise, decompose and become
unstable at sizes tens times larger.
This poor stability of these materials has been the
fundamental barrier to their use in future electronic devices – and this has
threatened to limit the future development of microelectronics.
"We have made ribbons only a few nanometres wide and
cannot rule out the possibility of confining graphene even further – down to
maybe a single ring of carbon atoms," says Professor Geim.
The research team suggests that future electronic circuits
can be carved out of a single graphene sheet. Such circuits would include the
central element or 'quantum dot', semitransparent barriers to control movements
of individual electrons, interconnects and logic gates – all made entirely of
graphene.
Geim's team have proved this idea by making a number of
single-electron-transistor devices that work under ambient conditions and show
a high-quality transistor action.
"At the present time no technology can cut individual
elements with nanometre precision. We have to rely on chance by narrowing our
ribbons to a few nanometres in width," says Dr Leonid Ponomarenko, who is
leading this research at The University of Manchester. "Some of them were too
wide and did not work properly whereas others were over-cut and broken."
But Dr Ponomarenko is optimistic that this proof-of-concept
technique can be scaled up.
"To make transistors at the true-nanometre scale is
exactly the same challenge that modern silicon-based technology is facing now.
The technology has managed to progress steadily from millimetre-sized
transistors to current microprocessors with individual elements down to tens
nanometres in size.
"The next logical step is true nanometre-sized circuits
and this is where graphene can come into play because it remains stable –
unlike silicon or other materials – even at these dimensions."
Professor Geim does not expect that graphene-based circuits
will come of age before 2025. Until then, silicon technology should remain
dominant.
But he believes graphene is probably the only viable
approach after the silicon era comes to an end.
"This material combines many enticing features from
other technologies that have been considered as alternatives to the silicon-based
technology.
"Graphene combines most exciting features from
carbon-nanotube, single-electron and molecular electronics, all in one."
