Researchers highlight graphene's ballistic transport property
A recent study has revealed that graphene nanoribbons possess a property that could pave the way for novel types of electronic devices. Using electrons more like photons could provide the groundwork for a new class of electronic device that would exploit the ability of graphene to carry electrons with almost no resistance even at room temperature, a property known as ballistic transport.
Walt de Heer, a Regent's professor in the School of Physics at the Georgia Institute of Technology, poses with equipment used to measure the properties of graphene nanoribbons. De Heer and collaborators from three other institutions have reported ballistic transport properties in graphene nanoribbons that are about 40nm wide. (Georgia Tech Photo: Rob Felt)
The study shows that electrical resistance in nanoribbons of epitaxial graphene changes in discrete steps following quantum mechanical principles. The research also reveals that the graphene nanoribbons act more like optical waveguides or quantum dots, allowing electrons to flow smoothly along the edges of the material. In ordinary conductors such as copper, resistance increases in proportion to the length as electrons encounter more and more impurities while moving through the conductor.
The ballistic transport properties, similar to those observed in cylindrical carbon nanotubes, exceed theoretical conductance predictions for graphene by a factor of 10. The properties were measured in graphene nanoribbons approximately 40nm wide that had been grown on the edges of 3D structures etched into silicon carbide wafers.
"This work shows that we can control graphene electrons in very different ways because the properties are really exceptional," said Walt de Heer, a Regent's professor in the School of Physics at the Georgia Institute of Technology. "This could result in a new class of coherent electronic devices based on room temperature ballistic transport in graphene. Such devices would be very different from what we make today in silicon."
The research was done through a collaboration of scientists from Georgia Tech in the US, Leibniz Universitat Hannover in Germany, the Centre National de la Recherche Scientifique (CNRS) in France and Oak Ridge National Laboratory, supported by the Department of Energy, in the US.
For nearly a decade, researchers have been trying to use the unique properties of graphene to create electronic devices that operate much like existing silicon semiconductor chips. But those efforts have met with limited success because grapheme, a lattice of carbon atoms that can be made as little as one layer thick, cannot be easily given the electronic bandgap that such devices need to operate.
De Heer stated that researchers should stop trying to use graphene like silicon, and instead use its unique electron transport properties to design new types of electronic devices that could allow ultra-fast computing based on a new approach to switching. Electrons in the graphene nanoribbons can move tens or hundreds of microns without scattering.