Boffins working at Rensselaer Polytechnic Institute have worked out how to use water to tune the band gap of the nanomaterial graphene. The breakthrough opens the door to new graphene-based transistors and nanoelectronics.

Rensselaer Professor Nikhil Koratkar and his research team worked out that if they exposed a graphene film to humidity, they could create a band gap in graphene. This has been the barrier to creating graphene transistors and end the need for semiconducting material made of silicon.

Graphene is an atom-thick sheet of carbon atoms arranged like a nanoscale chain-link fence, Normally it has no band gap. Koratkar’s team worked out how to open a band gap in graphene based on the amount of water they adsorbed to one side of the material, precisely tuning the band gap to any value from 0 to 0.2 electron volts. It was fully reversible and the band gap was reduced back to zero under vacuum. The good part about it, was that the technique does not involve any  complicated engineering or modification of the graphene, but requires an enclosure where humidity can be precisely controlled.

According to the Journal Small, which we get for the electron microscope “spot the ball” competition in its natural state, graphene has a peculiar structure but no band gap. Semiconductors have a narrow band gap, and application of an electric field can provoke electrons to jump across the gap. The ability to quickly switch between the two states — “on” and “off” — is why semiconductors are so valuable in microelectronics. Koratkar said that at the heart of any semiconductor device is a material with a band gap,. Chips and microprocessors in today’s cell phones, mobile devices, and computers, each contains a multitude of transistors made from semiconductors with band gaps. But Graphene is a zero band gap material, which limits its use. By coming up with methods to induce a band gap in graphene to make it a relevant semiconducting material.”