New Technique May Enhance the 'Wonder Material' Graphene: Winding Borders

There may be a new technique to enhance graphene. Scientists have found that a winding thread of odd rings at the border of two sheets of graphene has qualities that could be valuable to manufacturers.

Graphene is the new "wonder material" of materials science. It's an atom-thick form of carbon, and rarely appears as a perfect lattice of chicken wire-like six-atom rings. Instead, it usually consists of "domains," or separately grown sheets the bloom outward from hot catalysts until they meet up.

When the regular rows of atoms meet, they aren't necessarily aligned. This means they have to adjust if they are to form a continuous graphene plane. This adjustment appears as a grain boundary with irregular rows of five and seven-atom rings that compensate for the angular disparity.

In the past, researchers believed that these rings with seven carbon atoms would be weak spots and actually impair the graphene material. Now, though, new research shows otherwise.

The researchers calculated the mechanical strength of grain boundaries to see how they influenced each other. Grain boundaries could minimize the interface energy between sheets by forming pairs of rings called dislocations, where an atom shifts from one six-member ring to its neighbor to form connected five- and seven-atom units.

The researchers created simulations of these boundaries to measure their strength and band-gap properties. In the end, they found that one of the simulations of energetically "preferred" sinuous grain boundaries was a near-perfect match for an asymmetric boundary that was detailed in a previous study. The scanning transmission electron microscopy image showed an atomic grain-boundary structure with very similar arrangement of dislocations.

So what does this mean? It's possible that, under certain conditions, these rings could actually benefit graphene. To take advantage of the predictions, though, scientists would have to figure out how to grow polycrystalline graphene with precise misalignment of the components.

The findings are published in the journal Advanced Functional Materials.

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