Stacking graphene changes its electrical properties

R&D Magazine : Stacking up three layers of graphene can significantly modify its electrical properties, according to research at the University of California, Riverside. Depending on how the three layers are stacked, some structures are conducting and some are insulating. Graphene is a one-atom-thick sheet of carbon atoms, arranged in hexagonal rings. Its most stable, conducting form occurs when one corner of the hexagons of the middle sheet is located above the center of the hexagons of the bottom sheet, and the top sheet is exactly on top of the lowest sheet, forming what’s called a Bernal-stacked trilayer, or ABA pattern. If the top sheet is shifted by the distance of a single atom, to a rhombohedral-stacked trilayer, or ABC pattern, the trilayer arrangement becomes insulating. “Why this happens is not clear as yet. It could be induced by electronic interactions. We eagerly await an explanation from theorists!” said Jeanie Lau, one of the authors of a Nature Physics paper on the subject.