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A new method to produce large, monolayer single-crystal-like graphene films more than a foot long relies on harnessing a "survival of the fittest" competition among crystals. The novel technique, developed by a team led by the Department of Energy's Oak Ridge National Laboratory, may open new opportunities for growing the high-quality two-dimensional materials necessary for long-awaited practical applications.

Making thin layers of graphene and other 2D materials on a scale required for research purposes is common, but they must be manufactured on a much larger scale to be useful.

Graphene is touted for its potential of unprecedented strength and high electrical conductivity and can be made through well-known approaches: separating flakes of graphite—the silvery soft material found in pencils—into one-atom-thick layers, or growing it atom by atom on a catalyst from a gaseous precursor until ultrathin layers are formed.

The ORNL-led research team used the latter method—known as chemical vapor deposition, or CVD—but with a twist. In a study published in Nature Materials, they explained how localized control of the CVD process allows evolutionary, or self-selecting, growth under optimal conditions, yielding a large, single-crystal-like sheet of graphene.

"Large single crystals are more mechanically robust and may have higher conductivity," ORNL lead coauthor Ivan Vlassiouk said. "This is because weaknesses arising from interconnections between individual domains in polycrystalline graphene are eliminated."

"Our method could be the key not only to improving large-scale production of single-crystal graphene but to other 2D materials as well, which is necessary for their large-scale applications," he added.

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Category: Science