http://www.physorg.com/news91891899.html

New graphene transistor promises life after death of silicon chip

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.
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."

Source: University of Manchester

-- 

Ken

"Buddhism elucidates why we are sentient."
"Buddhism follows thought throughout the Universe."
"Karma means that you don't get away with anything."