Band gap - Page 8

Researchers from the Rensselaer Polytechnic Institute has developed a new method to open and tune the band gap of Graphene - using water. By exposing the Graphene film to humidity, the researchers created the band gap. A band gap is required to create transistors, so this can help pave the way for Graphene transistors.

The researchers found out that by changing the amount of water absorbed on one side of the Graphene film, they can tune the band gap to any value from 0 to 0.2 electron volts, and this is reversible under vacuum.

A group of scientists from Germany, China and the US has created a Graphene-based transistor composed of 13 benzene rings. This molecule (called Coronene) shows an improved electronic band gap, a property which may help to overcome one of the central obstacles to applying graphene technology for electronics.

The team's new approach to make graphene is bottom up—building up the graphene, molecular piece by piece. To do this, Tao relies on the chemical synthesis of benzene rings, hexagonal structures, each formed from 6 carbon atoms. "Benzene is usually an insulating material, " Tao says. But as more such rings are joined together, the material's behavior becomes more like a semiconductor.

Researchers from UCLA has created a new Graphene nanostructure called Graphene nanomesh (GNM). The new structure is able to open up a band gap in a large sheet of graphene to create a highly uniform, continuous semiconducting thin film that may be processed using standard planar semiconductor processing methods.

The nanomesh can have variable periodicities, defined as the distance between the centers of two neighboring nanoholes. Neck widths, the shortest distance between the edges of two neighboring holes, can be as low as 5 nanometers. This ability to control nanomesh periodicity and neck width is very important for controlling electronic properties because charge transport properties are highly dependent on the width and the number of critical current pathways.

IBM Researchers has opened a bandgap for graphene field-effect transistors (FET) that could someday rival complementary metal oxide semiconductor. This is one of the last roadblocks to commercialization of Graphene-based technology, according to IBM.

Graphene has a higher carrier mobility than Silicon, but lacks a band gap, which has kept the on-off ratio of graphene transistors dismally low—usually less than 10 compared to hundreds for silicon. Now IBM says that they have managed to create a tunable electrical bandgap (up to 130meV) for their bi-layer graphene FETs. And larger bandgaps are possible, too.