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IBM
scientists discover graphite as a material for building
nanoelectronic circuits
Other topics:
Nanotechnology Television Series
IBM
March 6,2008
Atomic-Sized Graphene Double Layer Holds Nanoelectronics
Promise
Yorktown Heights, NY -- IBM (NYSE: IBM) Researchers today
announced a discovery that combats one of the industry's
most perplexing problems in using graphite -- the same
material found inside pencils -- as a material for building nanoelectonic circuits vastly smaller than those found in
today's silicon based computer chips.
IBM'S ATOMIC 'CHICKENWIRE' FOR NANO ELECTRONICS: The image
on the left shows a single layer, or sheet of carbon
molecules known as Graphene. The noise that occurs from
electrical signals bouncing around in the material as a
current is passed through it is greater as the device is
made smaller and smaller, impeding the performance for
nanoscale electronics. In the image on the right, the IBM
scientists demonstrated for the first time that adding a
second sheet of Graphene reduces the noise significantly,
giving promise to this material for potential use in future
nanoelectronics.
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For the first time anywhere, IBM scientists have found a way
to suppress unwanted interference of electrical signals
created when shrinking graphene, a two-dimensional,
single-atomic layer thick form of graphite, to dimensions
just a few atoms long.
Scientists around the world are exploring the use of
graphene as a much smaller replacement for today's silicon
transistors. Graphene is a two-dimensional honeycomb lattice
of carbon atoms, similar to atomic-scale chicken-wire, which
has attracted strong scientific and technological interest
because it exhibits promising electrical properties and
could be used in transistors and circuits at scales vastly
smaller than components inside of today's tiniest computer
chips.
One problem in using these nano-devices is the inverse
relationship between the size of the device and the amount
of uncontrolled electrical noise that is generated: as they
are made smaller and smaller, the noise -- electrical
charges that bounce around the material causing all sorts of
interference that impede their usefulness -- grows larger
and larger. This trend is known as Hooge's rule, and occurs
in traditional silicon based devices as well as in graphene
nano-ribbons and carbon nanotube based devices.
"The effect of noise from Hooge's rule is exaggerated at the
nanoscale because the dimensions are approaching the nearly
smallest limits, down to only a handful of atoms, and the
noise that is created can overwhelm the electrical signal
that needs to be achieved to be useful," said IBM Researcher
Dr. Phaedon Avouris, who leads IBM's exploration into carbon
nanotubes and graphene. "To quote the famous physicist Rolf
Landauer, at the nanoscale 'the noise is your signal'; in
other words, you cannot produce any useful electronic device
at the nanoscale if the noise is comparable to the signal
you are trying to switch on and off."
Now, IBM scientists have found that the noise in graphene-based
semiconductor devices can, in fact, be suppressed and report
the results today in the journal Nano Letters.
In their experiments, the IBM Researchers first used a
single layer, or sheet, of graphene to build a transistor
and noted that the device does in fact follow Hooge's Rule:
as they are made smaller and smaller, there is an increase
in the noise that is created.
Two Layers Are Better Than One
However, when the IBM Researchers built the same device with
two sheets of graphene instead of one -- one stacked on top
of the other -- they noted that the noise is suppressed, and
is weak enough that these so-called bilayer graphene ribbons
could prove useful for building future semiconductor devices
for use in sensors, communications devices, computing
systems and more. The noise is inhibited because of the
strong electronic coupling between the two graphene layers
that counteracts the influence of the noise sources: the
system acts as a noise insulator.
While further detailed analysis and studies are required to
better understand these phenomena, the findings provide
exciting opportunities for graphene bilayers in a variety of
applications. |
