This tells us that full blown graphene fabrication and manufacturing
integration is well on the way to achieving it's natural promise. Yet
it is barely into public awareness even several years after it
arrived on the scene.
I also think that manufacturing is barely beginning to master this
product and expect to see astonishing things here not possible on
anything else.
We can see decades of advances coming into this easily equal to what
was experienced with silicon.
Flexible graphene
transistor sets new records
Dec 10, 2012
Researchers at the
University of Texas at Austin in the US say that they have made
state-of-the-art flexible graphene field-effect transistors with
record current densities and the highest power and conversion gain
ever. The transistors also show near-symmetric electron and hole
transport, are the most mechanically robust flexible graphene devices
fabricated to date, and can be immersed in a liquid without any ill
effects.
Graphene is a single,
flat sheet of carbon arranged in a honeycombed lattice. It has many
unique electronic and mechanical properties, such as extremely high
carrier mobility – which means that it is an ideal material for use
in ultrafast transistors. The material can also absorb light over a
range of wavelengths in the electromagnetic spectrum from the visible
to mid-infrared and is highly transparent to light. The fact that it
is mechanically flexible while being incredibly strong is good news
too.
The researchers, led
by Deji Akinwande and Rodney Ruoff, made their graphene field-effect
transistors (GFETs) directly atop patterned dielectrics on plastic
sheets using conventional microelectronic lithography. The devices
have a unique structure, explains Akinwande, in which multi-finger
metal gate electrodes are embedded in the plastic sheet. They are
also made using graphene that has been grown by chemical vapour
deposition (CVD), which can now produce as good graphene flakes as
can be obtained by exfoliation (the famous "sticky-tape"
method).
Record properties
The innovative
production technique means that graphene can easily be integrated and
fabricated on plastic sheets that have been pre-patterned with metal
gates. This produces transistors in which charge carriers can move
extremely fast and in which electrons and holes move in the same way.
The devices are also extremely compliant and can accommodate
mechanical strains of up to 9% and can be bent and unbent over for
more 20 continuous cycles – a record number for flexible
GFETs.
"Overall, our
transistors feature record circuit performance, the largest
mechanical bending and the highest extrinsic cut-off frequencies (of
about 2.23 GHz) to date for any graphene flexible nanoelectronic
device," says Akinwande. "What is more, the devices are
liquid-resistant thanks to the fact that the surface of the graphene
is passivated with silicon nitride and the plastic substrate is
self-passivated. In short, we found that they could be
accidentally dropped into everyday liquids, such as milk, tea or
coffee, and can even survive being run over by a moving vehicle –
all without suffering damage to their outstanding properties."
Smart applications
The extremely
flexible, high-performance devices could be ideal for smart,
conformal, advanced electronics that could offer performance
capabilities beyond today’s silicon-based technology while also
being cheaper, lighter, more environmentally friendly and with
arbitrary form factors, claims Akiwande. "Potential applications
include flexible smartphones, displays, fabric and even smart walls,"
he adds.
The team, which is
presenting its work this week at the International Electron Devices
Meeting in San Francisco, is now busy trying to make flexible
wireless radios and mobile systems using the new GFETs at gigahertz
frequencies. "From a basic research point of view, we are also
looking into heat management in these devices on flexible plastic
substrates, which is a major issue for transistors operating at high
speeds and current densities," adds Akinwande.
About the author
Belle Dumé is a
contributing editor to nanotechweb.org
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