Technique paves way for defect-free graphene

The team, led by the University of Oxford, uncovered that tiny flakes of graphene form with random orientations when processed using chemical vapour deposition, leaving defects or seams between flakes that grow together. The discovery reveals how these graphene flakes, known as domains, can be lined up by manipulating the alignment of carbon atoms on a relatively cheap copper foil; the atomic structure of the copper surface acts as a guide that controls the orientation of the carbon atoms growing on top of them. 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 project leader Professor Nicole Grobert, of Oxford University's Department of Materials. "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." The team has shown that it is also possible using the new technique to selectively grow bi-layer domains of graphene – a double layer of closely packed carbon atoms – which are of particular interest for their unusual electrical properties. Prof Grobert continued: "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. "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."