Innovative Graphene Inverters Work at Room Temperature

Scientists at the Purdue University announce the development of graphene inverters that work at room temperature, a considerable improvement from the past generation of such materials. The latter needed temperature as low as minus 196 degrees Celsius (minus 320ºFahrenheit) to operate.

An inverter is a critical building block of digital transistors that enables the conversion of direct current to alternating current. What makes the new achievement even more remarkable is the fact that the team created such a device for a 2D material that does not have a band gap.

The single-atom-thick carbon compound graphene has been touted as a potential replacement for silicon in electronic applications ever since it was first discovered in 2004. However, the fact that it does not have a band gap has stifled its wide-scale adoption in this area.

Graphene is a zero-band-gap material through its very nature, and fact remains that silicon has the necessary trait, whereas it did not. “The fact that graphene is a zero-band-gap material by nature has raised many questions in terms of its usefulness for digital applications,” Hong-Yan Chen explains.

The expert holds an appointment as a PhD student at Purdue, and was one of the researchers involved in the new work. He explains that the band gap is the energy difference between the valence and conduction bands that affect the behavior of electrons in any material.

When the correct band gap is achieved in a material, then transistors can be turned on or off, which is essential for computing. Until now, graphene inverters – a key component of transistors – could only work at low temperatures, but now they can be operated easily at room temperature.

By creating these devices, the researchers basically eliminated one of the most difficult hurdles plaguing the adoption of graphene as a potent replacement for silicon, says Chen, the study's leader.

“If graphene could be used in digital applications, that would be really important,” he says. Chen partnered with expert Joerg Appenzeller, who is a professor of electrical and computer engineering, and the scientific director of nanoelectronics, at the Purdue Birck Nanotechnology Center.

Details of the study are presented in a paper entitled “Complementary-Type Graphene Inverters Operating at Room-Temperature,” which was presented at the 2011 Device Research Conference. The meeting was held this June, in Santa Barbara, California.

By using the new inverters, the team concludes, it will become possible to move from using graphene for cell phones and military systems only to deploying it in consumer electronics and computers.