Graphene has been touted as the next silicon, but it is too conductive to be used in computer chips. A University of Manchester team led by Nobel laureates Professor Andre Geim and Professor Konstantin Novoselov has literally opened a third dimension in graphene research.
The scientists suggest using graphene not laterally (in plane) – as all previous studies did – but in the vertical direction. They used graphene as an electrode from which electrons tunneled through a dielectric into another metal - called a tunneling diode. Then they exploited a unique feature of graphene – that an external voltage can strongly change the energy of tunneling electrons. As a result they got a new type of a device – vertical field-effect tunneling transistor in which graphene is a critical ingredient.
Dr Leonid Ponomarenko, who spearheaded the experimental effort, said: “We have proved a conceptually new approach to graphene electronics. Our transistors already work pretty well. I believe they can be improved much further, scaled down to nanometer sizes and work at sub-THz frequencies.”
The Manchester team made the transistors by combining graphene together with atomic planes of boron nitride and molybdenum disulfide. The transistors were assembled layer by layer in a desired sequence. Such layered superstructures do not exist in nature. It is an entirely new concept introduced in the report by the Manchester researchers. The atomic-scale assembly offers many new degrees of functionality, without some of which the tunneling transistor would be impossible.
“It really offers endless opportunities both for fundamental physics and for applications. Other possible examples include light-emission diodes, photovoltaic devices, and so on,” said Professor Novoselov.