Theoretical physicists at Rice University have figured out how to custom-design graphene nanoribbons by controlling the conditions under which the nanoribbons are pulled apart to get the edges they need for specific mechanical and electrical properties, such as metallic (for chip interconnects, for example) or semiconducting (for chips).

The new research by Rice physicist Boris Yakobson and his colleagues appeared this month in the Royal Society of Chemistry journal Nanoscale.

Customized ripping

Perfect (pristine) graphene is conductive and looks like chicken wire, with each six-atom unit forming a hexagon, with edges that are zigzags like this: /\/\/\/\/\/\/\/\ .

Turning the hexagons 30 degrees makes the edges “armchairs,” with flat tops and bottoms held together by the diagonals, making the nanoribbons both semiconducting and more stable.

The researchers used density functional theory, a computational method to analyze the energetic input of every atom in a model system, to learn how thermodynamic and mechanical forces would accomplish the goal.

Their study revealed that heating graphene to 1,000 kelvin and applying a low but steady force along one axis will crack it in such a way that fully reconstructed 5–7 rings will form and define the new edges. Conversely, fracturing graphene with low heat and high force is more likely to lead to pristine zigzags.

Yakobson is Rice’s Karl F. Hasselmann Professor of Materials Science and NanoEngineering and a professor of chemistry.

The Air Force Office of Scientific Research and NASA funded the research.