Solving a Graphene Mystery
Graphene has many fantastic properties that would seem to make it an ideal material for use in electronics, but its lack of one property makes its use almost impossible. The material lacks what is known as a bandgap, which is essential for controlling the flow of current. Theoretically bilayer graphene should have a bandgap, but still acted like a conductor when tested. Researchers at Berkeley Lab appear to have found the reason for this behavior, which may eventually provide a solution to the problem.
A single layer of graphene is an atom-thick sheet of carbon atoms in a hexagonal pattern, and is very strong, flexible, and highly conductive. By stacking two layers together, the interaction between the electrons should create a region where no electron states exist, a bandgap, but whenever bilayer graphene has been tested, electrons still appear at those impossible energy levels. Using the Advanced Light Source, the Berkeley researchers found that the bandgap failed because of twists in the bilayer graphene, where the carbon atoms did not quite line up. All it takes is ten misaligned atoms in a square micrometer to disrupt the bandgap.
Currently the means of creating bilayer graphene are not able to prevent such small imperfections, but now we know how powerful these imperfections are. Aside from developing a new fabrication method, it may be possible to minimize the imperfections by creating smaller pieces of bilayer graphene.
Source: Berkeley Lab