Global Sources
EE Times-India
Stay in touch with EE Times India
 
EE Times-India > Manufacturing/Packaging
 
 
Manufacturing/Packaging  

Graphene to enable tunable electronic devices

Posted: 18 Jun 2009     Print Version  Bookmark and Share

Keywords:graphene  transistor  LED  tunable bandgap 

Today's transistors and LEDs are based on silicon and gallium arsenide semiconductors, which have fixed electronic and optical properties.

Now, researchers from the University of California at Berkeley have shown that a form of carbon called graphene has an electronic structure that can be controlled by an electrical field, an effect that can be exploited to make tunable electronic and photonic devices.

While such properties were predicted for a double layer of graphene, this is the first demonstration that bilayer graphene exhibits an electric field-induced, broadly tunable bandgap, according to principal author Feng Wang, UC Berkeley assistant professor of physics.

Feng Wang (left) and Yuanbo Zhang at an optics bench in Birge Hall, where they conduct their experiments on graphene.

Feng Wang (left) and Yuanbo Zhang at an optics bench in Birge Hall, where they conduct their experiments on graphene.

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—and it 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," Wang said.

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

Wang, post-doctoral fellow Yuanbo Zhang, graduate student Tsung-Ta Tang and their UC Berkeley and Lawrence Berkeley National Laboratory (LBNL) colleagues report their success in the June 11 issue of Nature.

"The fundamental difference between a metal and a semiconductor is this bandgap, which allows us to create semiconducting devices," said coauthor Michael Crommie, UC Berkeley professor of physics. "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. Since it was first isolated from graphite, the material in pencil lead, in 2004, it 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.

However, the property that makes it a good conductor—its zero bandgap—also means that it's always on.

"To make any electronic device, like a transistor, you need to be able to turn it on or off," Zhang said. "But in graphene, though you have high electron mobility and you can modulate the conductance, you can't turn it off to make an effective transistor."

1 • 2 Next Page Last Page



Comment on "Graphene to enable tunable electroni..."
Comments:  
*  You can enter [0] more charecters.
*Verify code:
 
 
Webinars

Seminars

Visit Asia Webinars to learn about the latest in technology and get practical design tips.

 

Go to top             Connect on Facebook      Follow us on Twitter      Follow us on Orkut

 
Back to Top