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In Bolotkin and Columbia's suspension technique, an ultra clean sheet of graphene is first deposited onto a semi-conductor substrate. Then gold posts are deposited to hold the sheet in place. Finally, using standard lithography techniques, most of the substrate is eteched away, leaving the sheet of graphene suspended freely.  (Source: Kirill Bolotkin)
What could be better than electrified microscopic chicken wire with fractional charges?

“There are two features that make graphene exceptional. First, its molecular structure is so resistant to defects that researchers have had to hand-make them to study what effects they have. Second, the electrons that carry electrical charge travel much faster and generally behave as if they have far less mass than they do in ordinary metals or superconductors,” explains Kirill Bolotkin, assistant professor at the Vanderbilt Department of Physics and Astronomy. But though everyone’s favorite chickenwire carbon crystal boasts such greatness, it is still not without its challenges for the scientific community.

For one, creating sheets of graphene, even as it has gotten much easier in the recent past, is still somewhat difficult. One cannot simply use a press to create a sheet of carbon. Fortunately, advances by groups using common ingredients like sheets of indium or camera flashes look promising not only for raw material for studies, but for pre-printed electronic circuits.

Though the strength of graphene is undoubtedly an area of interest, its peculiar electrical properties may be of more use to all industries. Unlike most other conductors, graphene retains its superior abilities all the way down to the molecular level. One day time will run out for silicon-based electronics and it may be this property of graphene that allows it to take up the reigns for further miniaturization of modern electronics.

Another property that sets it apart from metallic conductors is the way electrons flow through and the effective mass they carry. In metallic conductors, electrons have to find their way through a maze of electrical fields produced by the metal atoms. This causes them to be perceived as if they have more mass than a typical electron should. The effect is quite the opposite in graphene however -- the electrons act as if they have little to no mass while they move through the crystal lattice.

This lack of mass conforms to the same relativistic equations that are thought to govern the behavior of particles in a black hole and particle accelerators.  Scientists call this quantum electrodynamics, and until recently, it has been very difficult to study this effect in graphene, even knowing that the electrons behave similarly.

Bolotkin, in cooperation with researchers at Columbia University, have come up with a method for suspending a sheet of graphene (PDF) from gold posts using standard lithography techniques. The idea for this process came from the team’s realization that part of the reason they weren’t getting the results they were looking for was due to the sheet of graphene being used being in contact with whatever material it was being laid upon for study.

One property they had hoped to see was an enhanced fractional quantum Hall effect. In a fractional quantum Hall effect, the interaction of electrons on a two-dimensional plane, magnetic fields and low temperature create electrons that have fractional negative charges.

Previous efforts to study the effect required a sandwich of different semiconductors being cooled to within a degree of absolute zero, and this only approximated the effect of a two-dimensional sheet because the movement of the electrons was confined between the two semiconductors. Using their new technique, the Columbia group was able to use a true two-dimensional plane. The suspended sample was cooled to only six degrees Kelvin and when a magnetic field was applied, this fractional quantum Hall effect sprang to life just as they had predicted.

With this new technique for suspending sheets of graphene, many more such experiments should be possible for researchers. Unlocking the mysteries of both graphene itself and exotic quantum electricity and other effects will undoubtedly bring new ideas and creations to tables everywhere.

The Columbia group’s research has been published in the journal Nature.





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