These promising results have been published in an online edition of the journal Nature Nanotechnology. The research group at Linköping University of Technology, led by Professor Rositza Yakimova, together with a research group at Chalmers, led by Associate Professor Sergey Kubatkin at the Department of Microtechnology and Nanoscience, MC2, along with colleagues in the United Kingdom and Italy, has demonstrated that Swedish graphene offers a high degree of accuracy for quantum mechanical effects - something that is otherwise only achieved in well-established semiconductors such as silicon and gallium arsenide.
The speed of the electrons in silicon - which is currently used to manufacture processors - has reached its limit. In graphene the electrons are 100 times quicker than in silicon and research groups throughout the world are now attempting to produce the material with sufficiently high quality.
Previously it has only been possible to demonstrate promising features on small areas of graphene. In order to progress it must be possible to manufacture the material with a larger area in order to make wafers from which circuits can be constructed. The focus of the research is now on wafers of silicon carbide, where the silicon is removed from the surface leaving a layer of carbon atoms. The advantage is that sufficiently large wafers of silicon carbide are commercially available although ensuring that the graphene is evenly shaped and with sufficient quality over large areas has proved difficult.
"The measurements indicate an improvement of four orders of magnitude or 10,000 times greater accuracy than the best results that have been achieved using exfoliated graphene," says Sergey Kubatkin, Associate Professor at Chalmers University of Technology. The results provide the first resistance standard, i.e. a measure of electronic resistance that is dependent purely on natural constants and which functions at a temperature of 4.2 K. The two resistance standards that have existed up to now are based on silicon or gallium arsenide but only work at very low temperatures and are considerably more difficult to produce and use.
The material that has now been tested successfully is manufactured using a method developed by the Linköping team Rositza Yakimova, Mikael Syväjärvi and Tihomir Iakimov.
"This indicates that Swedish research is world class when it comes to producing new materials that offer sufficiently high performance for use in the electronics of the future," says Mikael Syväjärvi, Associate Professor at the Department of Physics, Chemistry and Biology.
Article: Quantum resistance standard based on epitaxial graphene by A. Tzalenchuk, S. Lara-Avila, A. Kalaboukhov, S. Paolillo, M. Syväjärvi, R. Yakimova, O. Kazakova, T.J.B.M. Janssen, V. Falko and S. Kubatkin. Nature Nanotechnology Advanced Online Publication, January 17, 2010.Sergey Kubatkin, associate professor, +46(0)31-772 5475, sergey.kubatkin(@)chalmers.se
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