The Story of Graphene
Graphene is a fascinating material with many potential applications that stem from its unusual properties. It was thought not to be stable in its free form until it was isolated in 2004 by researchers at The University of Manchester. This is the story of how that discovery came about and why the researchers involved won the Nobel Prize in physics for their work.
If we stack layers of graphene on top of one another they form graphite, which is found in every pencil lead. In fact anyone who has drawn a line with a pencil has probably made some graphene. It was first studied as a limiting case for theoretical work on graphite by Phillip Wallace as long ago as 1947. The fact that electric current would be carried by effectively massless charge carriers in graphene was pointed out theoretically by Gordon Walter Semenoff , David P. DeVincenzo and Eugene J. Mele in 1984 and the name “graphene” was first mentioned in 1987 by S. Mouras and co-workers to describe the graphite layers that had various compounds inserted between them forming the so-called Graphite Intercallation Compounds or GIC’s.
The term has also been used extensively in the work on carbon nanotubes which are effectively rolled up graphene sheets. Attempts to grow graphene on other single crystal surfaces have been ongoing since the 1970’s, but strong interactions with the surface on which it was grown always prevented the true properties of graphene being measured experimentally.
The work at Manchester begins
The fact that the properties of graphene had not yet been measured and that it was thought not to be stable in its free form intrigued Andre Geim so much that in late 2002 he asked a new PhD student to see how thin he make a piece of graphite by polishing it down. This did not lead to sufficiently thin slices of material, but developed into one of Andre’s “Friday evening experiments” for Kostya Novoselov who was working on another project at the time. The term “Friday evening experiment” was used to describe a set of off beat, interest driven experiments but cunningly disguised the actual amount of work required to get any results. Having discussed the problem with friends and colleagues it was suggested by Oleg Shklyarevskii, a senior fellow from Kharkov, Ukraine that the material he threw away on the tape that was used to peel graphite and expose a clean surface for studies in surface science was thinner than the material Andre’s student had produced by polishing.
A willing volunteer
Kostya volunteered to look at how thin the graphite flakes on the tape could be made. In 2003, Andre and Kostya succeeded in producing the first isolated graphene flakes and this work was published in 2004. That paper provided the inspiration for many groups around the world to redouble their efforts to study the properties of this material. Indeed, many groups sent students and postdocs to Manchester to learn how to make the material and much fevered work was done to explore the unusual electronic properties of graphene.
The first major result on the electronic properties was the anomalous quantum Hall effect in graphene reported around the same time by Andre and Kostya and by Philip Kim’s group at Columbia University in 2005. This effect is a direct indicator of the massless nature of the charge carriers which had been predicted back in 1984. The Manchester group went on to show that graphene exhibited the quantum Hall effect at room temperature which had not been seen in other materials, that it has extremely high carrier mobility so will be useful for fast electronic devices, and it can even be used to detect single molecule adsorption/desorption events and would therefore be useful in chemical sensors.
The 2010 Nobel Prize for Physics
Andre and Kostya were awarded the 2010 Nobel prize in physics for this work and are continuing to unveil new and exciting properties in graphene and other related two dimensional crystal materials.