Meet Graphene: The ‘Supermaterial’ with a Serious Electrical Dilemma
by LIDA TUNESI
Graphene is a so-called “supermaterial” made of a single layer of carbon atoms arranged in repeating hexagons, much like the appearance of honeycomb. It is chemically stable, highly elastic, biocompatible, and has been estimated to be between 100 and 200 times stronger than steel. Despite all this, graphene’s electronic properties need some tweaking before its potential can be fully exploited for use in devices.
A paper co-authored by Professor Maya Narayanan Nair of the Advanced Science Research Center at The Graduate Center, CUNY, presents a new way to overcome graphene’s electrical dilemma. The paper appears in IOPscience.
The researchers found that by growing graphene on an underlying patterned surface, they can create the electronic properties necessary for producing transistors, crucial parts of electronic devices. Transistors are currently made of silicon, but scientists say graphene transistors could lead to much faster computers than we have today.
In order to start moving and conducting electricity, the electrons in a material need to reach a higher energy level than normal. In insulators, which are materials that don’t conduct electricity well, the energy jump-up to this level is large, making it hard for electrons to reach it. In a material that conducts electricity easily, there is no energy jump, or gap, at all, and electrons can flow freely. Transistors sit in the middle. They are semiconductor devices, meaning their electrons need to cross a small gap before they can conduct electricity.
Graphene is normally a conductor so to make a viable transistor material, scientists need to give it an energy gap. To achieve this, Nair and her co-authors “grew” graphene on a nanopatterned surface made of the metal iridium. The process alters graphene’s energy levels to have the appropriate gap. The researchers used two methods—chemical vapor deposition and temperature-programmed growth—to build graphene on top of the iridium surface.
The chemical vapor deposition method created better results than the temperature-programmed growth, and the authors say is worth exploring further.