New mineral makes play for graphene's throne

Watch out graphene. Just a week after IBM said the two dimensional wonder-carbon would never fully replace silicon, graphene has yet more competition. According to scientists in Switzerland, mineral called Molybdenite might be even better at putting silicon out to pasture.

Like graphite Molybdenite is composed of two dimensional layers of atoms, and is similarly useful in lubricants. The Swiss researchers report now that it is also a very effective semiconductor, and unlike graphene, the layers of molybdenite have band gap.

Briefly, a band is an energy level an electron has ‘orbiting’ its home atom. There is a valence band, where the electron is confined to its atom, and then there is a conduction band – a level of energy at which an electron will move freely around a material. The gap between these two levels is the band gap. Too big a gap and you get an insulator, too small and you have no way of stopping the electrons from zipping around all over the show. (There is more to it. Read up a here.)

Last week IBM poured a big bucket of cold water on the graphene parade, saying that it would not totally replace silicon. Graphene does not have a band gap, the company explained, meaning that any transistors made from the sheets of carbon could never be fully switched off. (Too many zippy electrons.)

Molybdenite, on the other hand, has a band gap of 1.8eV, making it ideal, the researchers say, for building super efficient transistors which would consume 100,000 times less energy in their stand-by state.

The research, carried out at EPFL’s Laboratory of Nanoscale Electronics and Structures, is published online in the January 30 edition of Nature Nanotechnology.