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UK research offers breakthrough in understanding graphene's electronic properties

29 January 2013

Research on the electronic properties of the super-material graphene could bring us one step closer to taking it from the laboratory to developing it for use in commercial products.

SuperSTEM2. There are only six of these exceptionally sensitive instruments worldwide (photo credit: SuperSTEM Consortium)
SuperSTEM2. There are only six of these exceptionally sensitive instruments worldwide (photo credit: SuperSTEM Consortium)

Scientists at the SuperSTEM facility at the UK Science and Technology Facilities Council’s Daresbury Laboratory have, for the first time, been able to observe changes to the electronic structure of graphene as it is bonds with a foreign element added to it just one atom at a time.

One important issue that must be addressed before graphene can be applied to a commercial product is that it lacks a feature called a ‘band gap’, which means that, in practice, it would be almost impossible to 'switch off' an electronic transistor based on pure graphene. One of the promising ways to engineer a band gap in graphene and overcome this limitation is through chemical modification, known as doping.

However, as a two-dimensional material, graphene is all surface and is therefore completely exposed to its environment and strongly affected by its surroundings. The minutest of structural variations can have tremendous effects on its properties.

Led by SuperSTEM’s Professor Quentin Ramasse, along with researchers from the Universities of Leeds and Manchester, the team has now been able to observe the minutest of variations that occur when a sheet of graphene is doped with a single atom of silicon.

Professor Quentin Ramasse, Scientific Director at SuperSTEM, said: “What we have shown here is not about what particular atom graphene should be doped with to harness its electrical properties, but that we have the capability to see, in the minutest detail, exactly how a single foreign atom integrates within the graphene - whether it slots in seamlessly, or whether it is distorting the graphene lattice by as little as 10 trillionths of a metre, and importantly how the distortions and precise bonding arrangement influence the electronic structure of that atom and of its environment.

"Such minute changes in bonding of these elements can in turn significantly affect the macroscopic behaviour of the graphene sheet, and particularly its electrical response, so it is essential to be able to quite literally fingerprint the bonding of these materials, one atom at a time. This could pave the way for research to identify which atoms will bond with graphene most appropriately. You might say that this marks the start of experimental physical chemistry at the single atom level.”

The precise characterisation of the bonding of single atoms is essential for the development of practical applications of two-dimensional materials, such as graphene.  In December the Chancellor, George Osborne, announced £21.5m in funding via the EPSRC to the most promising graphene-related research projects in UK universities, in plans to boost the ‘manufacturability’ of graphene. 

The results of this work are published in the journal, Nano Letters.

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