Revolutionising electronics through graphene

Graphene has the potential to change the world of electronics in much the same way that transistors and integrated circuits did last century. But use of this wonder material is still very much in the development stage in many laboratories and research centres around the world and, while promises are high, the widespread practical use of graphene is proving elusive.

At the pinnacle of research is the British $92m institute now being built at Manchester University, the home of graphene discovery. All eyes are now on the completion of this facility in 2014 to speed up the practical use of this substance that has taken the electronics industry by storm.

Australia, too, is contributing to the knowledge bank of graphene. Scientists at the CSIRO and the Royal Melbourne Institute of Technology have already worked out a way to make high-speed electronics possible.

This fits in well with other researchers around the world who are working on a variety of projects, all designed to bring graphene to commercial adoption as soon as possible. Some of their efforts include a graphene-based, highly conductive ink that is tolerant to bending, which has been developed at Northwestern University, a private research facility in the US. Patterns have been printed that could be used for highly detailed conductive electrodes. Although this is a promising use of the material, it is not without its challenges. The difficulty of gathering sufficient graphene without compromising its electronic properties still have to be overcome.

The Northwestern researchers printed the ink in 14 nm thick layers to make up precise patterns. Conductivity remained virtually unchanged, even when severely bent, indicating that graphene inks could, in future, be used to make foldable devices.

In another development, workers at MIT in the US, have suggested a system that combines ferroelectric materials with graphene to create computer and data-storage chips that contain more components in a given area, are faster and less power hungry.

The system would create a new way to build interconnected devices that use light waves such as fibre-optic cables and photonic chips with conventional wires and devices. At present, interconnection points form a bottleneck that slows data transfer and increases the component count.

The MIT system works by controlling waves known as surface plasmons. The waves, at terahertz frequencies, are oscillations of electrons confined at interfaces between materials. The waves can be concentrated at much smaller-length scales which could lead to a tenfold gain in the density of components that could be placed in the given area of a chip. The system may create a new way of reading and writing electronic data into ferroelectronic memory devices at very high speeds.

In another project, researchers are looking to produce the thinnest, most lightweight and efficient solar cell possible. Panels of one molecule thick materials such as graphene or molybdenum disulfide are at the heart of this work.

Using two layers of material, it is predicted that cells with 1 to 2% efficiency could convert sunlight to electricity. This is a low conversion rate compared with the current 15 to 20% efficiency of silicon cells but the new material is just 1 nm thick, about 50 times thinner than silicon and weighs thousands of times less than silicon.

Kilogram for kilogram the new cells produce up to 1000 times more power than present photovoltaics and, because the material is less expensive than silicon, only tiny quantities of material are needed.

At the Ulsan National Institute of Science and Technology in South Korea, graphene has been combined with silver nanowires to form a thin, transparent stretchable electrode. This, it is claimed, overcomes the weaknesses of each individual material, producing a new class of electrode with possible applications in picture taking and scanning using soft contact lenses. The electrode points the way towards flexible displays, improved solar cells and electronics generally.

Semiconductors grown on graphene are being researched at the Norwegian University of Science and Technology in Trondheim. While LEDs are superior in terms of energy efficiency, they are expensive to produce because of the costly semiconductor substrate.  Semiconductor nanowires as graphene are expected to make it possible to construct LEDs that are cheaper and more efficient, more pliable and lighter than today's devices.

Meanwhile in the US at Rice University and Oak Ridge National Laboratory, scientists have developed a method to control the growth of uniform atomic layers of molybdenum disulfide with the hope of joining it to graphene. If the union is possible, it will have hexagonal boron nitride added, which is an insulator, to create field effect transistors, integrated logic circuits, photodetectors and flexible optoelectronics.

Graphene is opening up all sorts of electronic possibilities. It is a material that is increasingly being combined with other substances. The threshold of its potential uses and applications has only just been crossed.