Tunnelling  transistor on vertical graphene heterostructures.

Yes,  graphene is now hailed as the vertical field effect tunnelling transistor  (VFETT)  as despite being too conductive to be used  a lateral fashion in computer chips, Manchester  University laureates Professors Andre Geim and Konstantin Novoselov open a third vertical dimension to show a transistor that may prove the missing link for graphene to become the next silicon. 

They 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 a device – vertical field-effect tunnelling VFET transistor in which graphene is a critical ingredient.

Dr Leonid Ponomarenko (left) 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 nanometre sizes and work at sub-THz frequencies.”

“It is a new vista for graphene research and chances for graphene-based electronics never looked better than they are now,” adds Novoselov.

Manchester team made the transistors by combining graphene with atomic planes of boron nitride and molybdenum disulfide. The transistors were assembled layer by layer in a desired layer sequence. The atomic-scale assembly offers many new degrees of functionality.

“The demonstrated transistor is important but the concept of atomic layer assembly is probably even more important,” says Geim. Novoselov adds:  “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.”

DEFECTS MAKE ANTENNAE
Right: Electron microscopy at Oak Ridge National Laboratory has demonstrated that silicon atoms (seen in white) can act like "atomic antennae" in graphene and transmit an electronic signal at the atomic scale.

A team of researchers from the US Department of Energy’s Oak Ridge National Laboratory (ORNL http://www.ornl.gov/ ) has shown that single-atom silicon defects in sheets of graphene act like atomic antennae, turning graphene into a plasmonic device capable of converting optical signals into electronic signals and vice versa. Dimension involved are two sheets of graphene connected by a two-atom silicon wire of some 0.1nm in diameter.

Electron microscopy at Oak Ridge National Laboratory has demonstrated that silicon atoms (seen in white) can act like "atomic antennae" in graphene and transmit an electronic signal at the atomic scale.

"In this proof of concept experiment, we have shown that a tiny wire made up of a pair of single silicon atoms in graphene can be used to convert light into an electronic signal, transmit the signal and then convert the signal back into light," said coauthor (left) Juan-Carlos Idrobo, holding a joint appointment at ORNL and Vanderbilt University.

AUSTRALIA FINDS GRAPHENE:CARBON FIBRE RATIO
SEM images of the fibre, shows well oriented  graphene and nanotubes in a 1:1 ratio in wet spun hybrid fibre.

At the University of Wollongong in New South Wales co-author of the study and polymer scientist GeoffSpinks said "We were able to find the 'magic ratio' of equal parts of carbon nanotubes and graphene added to polymer that worked really well and we produced really tough fibres." 

The researchers produced a solution of reducing graphene oxide nanoparticles, mixed it with separate solution of carbon nanotubes and 'injected' into a polymer solution of polyvinal alcohol (PVA).

Spinks said that upon injecting the two solutions into the polymer the "polymer molecules wrap around the graphene and nanotube particles and produce a solid material. And because it is injected as a stream it forms a long thick fibre."

When producing nano fibres, the process of 'wet-spinning' determines the structure of the fibres. By controlling the spinning conditions, the alignment of the units (in this case - polymer, graphene and nanotube particles) reflect the required properties like strength or toughness.

The researchers were able to get the nanotubes and graphene pointing in the same direction to increase strength. If the position of the polymer was in the same direction there would be no extra stretch and it would break easily. "We were able to align the nanotubes and the graphene but the polymer matrix PVA was still largely unaligned and that means it was able to stretch to where we wanted it to," said  (left) Spinks.

The new fibres of graphene and carbon nanotubes, described as "super tough" in the paper, approached a 'toughness' measurement of 1000 J/g, far exceeding other fibre materials. Graphene makes the production of the fibres more cost effective as graphene is a much cheaper material than carbon nanotubes and can be produced in large quantities quite easily.