Researchers in the U.K., Germany, and Greece developed a method of forming graphene layers with uniform orientation and alignment, using established and inexpensive techniques. The team led by University of Oxford materials scientist Nicole Grobert published its findings online last week in the journal ACS Nano (paid subscription required).
Grobert (pictured right), with colleagues from Oxford, German research institute Forschungszentrum Juelich, University of Ioannina in Greece, and British instrumentation company Renishaw plc, attacked a problem with growing graphene, namely the random alignment of the graphene flakes, called domains, that leave seams or defects in the material. These defects weaken the graphene and prevent electrons from flowing freely through the material, thus limiting its potential benefits.
Graphene is closely related to graphite like that used in pencils, but consists of only a single atomic layer of carbon atoms. The material is very light, strong, chemically stable, and can conduct both heat and electricity, with applications in fields such as electronics, energy, and health care.
Grobert and colleagues adapted chemical vapor deposition, an industrial technique for applying solid thin-film coatings to surfaces, particularly with high purity bulk materials. The researchers were able to align the graphene domains applied with chemical vapor deposition using relatively inexpensive copper foil. The atomic structure of the copper helps guide the orientation of the carbon atoms as they grow on the copper.
The team employed a combination of this copper guide and pressure to grow graphene with greater uniformity, controlling not only the alignment of the grain boundaries that can create the unwanted seams, but also the the thickness of these domains and the geometry of their edges. The size of graphene sheet that can be created, say the researchers, is only limited, at least in principal, by the size of the base sheet of copper base used to grow the graphene.
Grobert calls the findings “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.” She notes that, “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.”
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