Bilayer graphene to pave way for tunable electronic devices

June 11th, 2009 - 11:53 am ICT by ANI  

London, June 11 (ANI): Researchers at the University of California, Berkeley, have shown that a form of carbon called graphene has an electronic structure that can be controlled by an electrical field, a finding that may pave the way for a host of tunable electronic and photonic devices-such as transistors, LEDs and lasers.

Principal author Feng Wang, UC Berkeley assistant professor of physics, claims that this is the first ever demonstration that bilayer graphene exhibits an electric field-induced, broadly tunable bandgap.

The bandgap of a material is the energy difference between electrons residing in the two most important states of a material-valence band states and conduction band states.

The bandgap determines the electrical and optical properties of the material.

“The real breakthrough in materials science is that for the first time you can use an electric field to close the bandgap and open the bandgap. No other material can do this, only bilayer graphene,” Nature magazine quoted Wang as saying.

Tuning the bandgap of bilayer graphene can turn it from a metal into a semiconductor. Thus, a single millimeter-square sheet of bilayer graphene could potentially hold millions of differently tuned electronic devices that can be reconfigured at will.

“The fundamental difference between a metal and a semiconductor is this bandgap, which allows us to create semiconducting devices,” said co-author Michael Crommie, UC Berkeley professor of physics.

He added: “The ability to simply put a material between two electrodes, apply an electric field and change the bandgap is a huge deal and a major advance in condensed matter physics, because it means that in a device configuration we can change the bandgap on the fly by sending an electrical signal to the material.”

Graphene is a sheet of carbon atoms, each atom chemically bonded to its three neighbours to produce a hexagonal array that looks a lot like chicken wire.

And the material has been a hot topic of research, in part, because solid-state theory predicts unusual electronic properties, including a high electron mobility more than 10 times that of silicon.

“This is not just a technological advance, it also opens the door to some really new and potentially interesting physics,” said Crommie. (ANI)

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