A View from Katherine Bourzac
The Key to Graphene's Exotic Properties
Electrons moving through graphene behave as if they are massless.
As silicon is pushed to its limits, the semiconductor industry is looking to new materials to enable chips to keep getting faster. In one of these materials, a two-dimensional lattice of carbon atoms called graphene, electrons move about 100 times faster than they do in silicon at room temperature. Researchers have theorized about the origins of graphene’s exotic properties. Now they’re making strides in measuring the material’s properties at the subatomic level.
Graphene was first made in the lab only in 2004, and just last year, researchers determined that it is the strongest known material. Knowing more about graphene’s electrical properties should help researchers who are trying to make reliable transistors and other devices from the material on a large scale. You won’t find graphene-based processors inside your laptop or cell phone until these manufacturing challenges are addressed.
Now a study published this week in the journal Science offers some insight into the origins of graphene’s fantastic electronic properties. Using a custom-built machine to perform an extremely high-resolution imaging technique called scanning-tunneling spectroscopy, researchers at Georgia Tech and the National Institute of Standards and Technology tracked the movement of electrons in the material. They found that in graphene, electrons behave somewhat like photons: while they don’t move at the speed of light, they do behave as if they are massless. The behavior of electrons looks stranger when the material is exposed to a strong magnetic field. In metals and other conventional materials, magnetic fields cause electrons to orbit in evenly spaced energy levels, but when graphene is put in a magnetic field, the electrons’ energy levels are unevenly spaced. It wasn’t possible to make measurements at this level of detail before because the quality of the graphene samples wasn’t high enough.