An international team of researchers, under the leadership of Cory Dean from Columbia University (New York, USA), has developed a technique for manipulating the electrical conductivity of graphene by compressing it. This achievement brings the graphene transistor a step closer.
Graphene is the best electrical conductor that we know; the problem is actually that it is too good a conductor – up to now there was no effective method for controlling the amount of conduction. The researchers, however, have succeeded in giving graphene and technically relevant band gap without reducing the quality.
Since the discovery more than 10 years ago, the unusual electrical properties of graphene, a two-dimensional material consisting of carbon atoms arranged in a hexagonal pattern, have excited physicists. Graphene is the strongest and, simultaneously, thinnest material known. Additionally it is a superior conductor: the unique arrangement of carbon atoms enables electrons to move easily and quickly with very low losses.
A holy grail for graphene researchers is to keep all the desirable characteristics of graphene but to also give it a band gap – that is, an on/off switch such as in a transistor. When graphene is sandwiched between layers of boron-nitride (BN, an insulator with a thickness of a single atom), the electron structure of the graphene can be changed such that a band gap forms – but this is not large enough to make a graphene transistor at room temperature possible.
The researchers however, have now discovered that when the layers of the BN/graphene structure are compressed, the size of the band gap increases considerably. This is nevertheless still not large enough for transistor functionality at room temperature, but thanks to this fundamental research potential practical applications are a little closer.
(Video: Toekomstmakers / RTL XL.)