03 February 2012
Graphene electronics breakthrough turns previous research on head
Scientists from the University of Manchester have opened a third dimension in graphene research, in a bid to address the problem of the material being too conductive to be used in computer chips.
The team, led by Nobel laureates, Prof Andre Geim and Prof Konstantin Novoselov, pictured, has discovered that a transistor that may prove the missing link for graphene to become the next silicon.
One of the potential applications of graphene is its use as the basic material for computer chips instead of silicon. While individual transistors with very high frequencies – up to 300GHz – have been demonstrated by other researchers, they can't be packed densely in a computer chip because they leak too much current, even in the most insulating state of graphene. This electric current would cause chips to melt within a fraction of a second and, until now, no real solution has been offered.
The University of Manchester scientists suggest using graphene not laterally (in plane) – as all previous studies did – but in the vertical direction. The researchers used graphene as an electrode from which electrons tunnelled through a dielectric into another metal – a 'tunnelling diode'. They then exploited a unique feature of graphene – that an external voltage can strongly change the energy of tunnelling electrons. As a result, they got a new type of device – vertical field effect tunnelling transistor in which graphene is a critical ingredient.
The researchers believe they have proved a conceptually new approach to graphene electronics and plan to improve the transistors even further, scaled down to nanometre sizes and able to work at sub THz frequencies.
The transistors were made by combining graphene together with atomic planes of boron nitride and molybdenum disulfide. They were then assembled layer by layer in a desired sequence. This concept is entirely new as such 'layer cake' superstructures do not exist in nature and, according to the researchers, the atomic scale assembly offers many new degrees of functionality, without some of which the tunnelling transistor would be impossible.
"It is a new vista for graphene research and chances for graphene based electronics never looked better than they are now," said Prof Novoselov. "Tunnelling transistor is just one example of the inexhaustible collection of layered structures and novel devices which can now be created by such assembly It really offers endless opportunities, both for fundamental physics and for applications. Other possible examples include light emission diodes, photovoltaic devices and so on."
Prof Geim added: "The demonstrated transistor is important, but the concept of atomic layer assembly is probably even more important."
Author
Chris Shaw
Supporting Information
Websites
http://www.manchester.ac.uk/
Companies
University of Manchester
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