Graphene can be fabricated using chemical vapour deposition but the method can lead to the creation of graphene flakes that are formed with random orientations, leaving defects or ‘seams’ between flakes that grow together.
The Oxford University-led discovery, reported in a paper to be published in ACS Nano, reveals how these graphene flakes (domains) can be lined up by manipulating the alignment of carbon atoms on a relatively cheap copper foil. This is because the atomic structure of the copper surface acts as a guide that controls the orientation of the carbon atoms growing on top of them.
According to the university, a combination of control of this copper guide and the pressure applied during growth makes it possible to control the thickness of these domains, the geometry of their edges and the grain boundaries where they meet — seams that act as obstacles to the smooth progress of electrons necessary to create efficient graphene-based electrical and electronic devices.
‘Current methods of growing flakes of graphene often suffer from graphene domains not lining up,’ said Prof Nicole Grobert of Oxford University’s Department of Materials, who led the work. ‘Our discovery shows that it is possible to produce large sheets of graphene where these flakes — called domains — are well-aligned, which will create a neater, stronger, and more electron-friendly material.’
In principle the size of the sheet of graphene that can be created is only limited by the size of the copper base sheet.
The Oxford-led team, which includes researchers from Forschungszentrum Juelich Germany, the University of Ioannina Greece, and Renishaw, has shown that it is also possible using the new technique to selectively grow bilayer domains of graphene — a double layer of closely packed carbon atoms — which are of particular interest for their unusual electrical properties.
‘People have used copper as a base material before, but this is the first time anyone has shown that the many different types of copper surfaces can indeed strongly control the structure of graphene,’ said Grobert in a statement. ‘It’s an important step towards finding a way of manufacturing graphene in a controlled fashion at an industrial scale — something that is essential if we are to bridge the gap between fundamental research and building useful graphene-based technologies.’
The team filed a UK patent application on the work in 2012 with the help of Isis Innovation, Oxford University’s technology transfer company.
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