Science and Technology Facilities Council
Future of fast computer chips could be in graphene and not silicon says new research
Scientists using lasers at a Science and Technology Facilities Council (STFC) facility in the UK believe that they are a step closer to finding a replacement for silicon chips that are faster and use less energy than at present.
The team has tested the behaviour of bilayer graphene to discover whether or not it could be used as a semiconductor. Their results suggest that it could replace silicon transistors in electronic circuits.
Graphene is pure carbon in the form of a very thin, almost transparent sheet, one atom thick. It is known as a ‘miracle material’ because of its remarkable strength and efficiency in conducting heat and electricity.
In its current form graphene is not suitable for transistors, which are the foundation of all modern electronics. For a transistor to be technologically viable, it must be able to ‘switch off’ so that only a small electric current flows through its gate when in standby state. Graphene does not have a band gap so cannot switch off.
The research team, led by Professor Philip Hofmann from Aarhus University in Denmark, used a new material – bilayer graphene – in which two layers of graphene are placed one on top of the other, leaving a small band gap to encourage the transfer of energy between layers.
Using Artemis at STFC’s Central Laser Facility, which is based at the Rutherford Appleton Laboratory in Oxfordshire, the researchers fired ultra-short pump laser pulses at the bilayer graphene sample, boosting electrons into the conduction band.
A second short, extreme ultraviolet, wavelength pulse then ejected electrons from the sample. These were collected and analysed to provide a snapshot of the energies and movement of the electrons.
“We took a series of these measurements, varying the time delay between the infrared laser pump and extreme ultraviolet probe, and sequenced them into a movie,“ said STFC’s Dr Cephise Cacho, one of the research team. “To see how the fast-moving electrons behave, each frame of the movie has to be separated by just a fraction of a billionth of a second.”
Professor Hofmann said, “What we’ve shown with this research is that our sample behaves as a semiconductor, and isn’t short-circuited by defects.”
There can be imperfections in bilayer graphene as the layers sometimes become misaligned.
The results of this research, in which the graphene showed no defects, suggest that further technological effort should be carried out to minimise imperfections. Once this is done, there is a chance that the switch-off performance of bilayer graphene can be boosted enough to challenge silicon-based devices.
Graphene transistors could make smaller, faster electronic chips than are achievable with silicon. Eventually more and more transistors could be placed onto a single microchip to produce faster, more powerful processors for use in electronic equipment.
STFC Press Officer
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Notes for editors:
The research paper Ultrafast Dynamics of Massive Dirac Fermions in Bilayer Graphene is published in Physical Review Letters.
It is also featured as a spotlight article in the American Physical Society’s Physics Viewpoint.
The Central Laser Facility (CLF) at the STFC Rutherford Appleton Laboratory is one of the world’s leading laser facilities providing scientists from the UK and Europe with an unparalleled range of state of the art technology. CLF is a partnership between its staff and the large number of members of UK and European universities who use the specialised laser equipment provided to carry out a broad range of experiments in physics, chemistry and biology. Artemis is the CLF’s facility for ultrafast laser and extreme-ultraviolet science.
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