The
world's smallest transistor
Researchers have built the world's smallest
transistor - one atom thick and 10 atoms wide - out of a material that could
one day replace silicon.
The transistor, essentially an on/off switch, has been made using graphene,
a two-dimensional material first discovered only four years ago.
Graphene is a single layer of graphite, which is found in the humble pencil.
The researchers are also looking at its use in
display technology - because it is transparent.
The Manchester-based scientists have shown that graphene can be carved
into tiny electronic circuits with individual transistors not much
larger than a molecule.
Dr Novoselov told BBC News that graphene had many advantages over
silicon because it could conduct electricity faster and further.
Leak electricity
The global semiconductor business is currently built on sand; stamping
out microchips from large silicon wafers.
Companies like Intel have a roadmap to reduce the size of circuits on
the silicon wafer, down to about 10 nanometres - 10,000 times smaller
than the width of a single human hair.
Many researchers believe that producing circuits smaller than 10
nanometres in silicon will be too difficult because they start to leak
electricity at that size.
That current silicon roadmap is expected to end in 2020, making the race
to find alternative materials potentially very lucrative.
Producing graphene sheets big enough to be used as wafers for chip
production remained the biggest hurdle, said Dr Novoselov.
"We can control the cut down to 20 nanometres. And then when we have to
scale down to one nanometre we use a bit of luck.
The yield of the working devices is about 50%
Many researchers around the world are working on creating large wafers
of graphene.
In order to produce microchips wafers would need to be several inches
across. The biggest wafer produced so far is 100 microns across, just a
tenth of a millimetre.
"I do believe we will find the technology to do this. And when we do
silicon will be replaced by graphene," said Dr Novoselov.
Professor Bob Westervelt, in an assessment of the material and its
future application in the journal Science, wrote: "Graphene is an
exciting new material with unusual properties that are promising for
nanoelectronics.
"The future should be very interesting."
Dr Novoselov added: "Given the material was first obtained by us four
years ago, we are making good progress."
He said the process of using graphene to build circuits was very
compatible with silicon technology.
"At the moment we use all the same steps to make a transistor as is done
by the silicon industry. So once we have large wafers of graphene it
should be straightforward to use the same process."
But it might be another 10 years before the first integrated circuits on
graphene chips appear, he said.
Shorter term
In the shorter term graphene could be used in LCD displays to replace
materials used to create transparent conductive coatings.
"The computer screen relies on good transparent conductors. But current
materials are expensive and hard to produce.
"Graphene is only one atom thin so is absolutely transparent - it's a
really wonderful conductor.
"We propose to use it as a transparent conductor, using small
interconnecting graphene sheets all together."
The material is also being touted for use in solar panels, transparent
window coatings and also for sensing technologies.
Dr Kostya Novoselov and Professor Andre Geim from The School of Physics
and Astronomy at The University of Manchester presented their findings
in the 17 April issue of Science.
"These transistors will work and work at ambient,
room temperature conditions - just what is required for modern
electronics," he said.
Dr Novoselov said graphene was a "wonderful conductor", making it a
perfect material for chip applications.
"It is already superior to silicon by an order of magnitude and
comparable to the best samples of other materials.
"We believe we can increase this mobility of electron flow 10-fold."
Graphene is a hot topic among semiconductor researchers at the moment
because it is an excellent conductor of electricity. Unlike silicon
graphene transistors perform better the smaller they become.
The transistor is the key building block of
microchips and the basis for almost all electronics.
Dr Kostya Novoselov and Professor Andre Geim from The School of Physics
and Astronomy at The University of Manchester have been leading research
into the potential application of graphene in electronics and were the
first to separate a sheet of the material from graphite
Super material
Graphene has been hailed as a super material
because it has many potential applications. It is a flat molecule, with
only the thickness of an atom, and both very stable and robust.
