Magneto-electric transistors promise low power future for non-silicon chips

Along with curbing the energy consumption of any microelectronics that incorporate it, the team’s design could reduce the number of transistors needed to store certain data by as much as 75 per cent leading to smaller devices.

It could also lend those microelectronics “steel-trap memory” that remembers exactly where its users leave off, even after being shut down or abruptly losing power

Many millions of transistors line the surface of every modern integrated circuit, or microchip. By regulating the flow of electric current within a microchip, the tiny transistor effectively acts as a nanoscopic on-off switch that’s essential to writing, reading and storing data as the 1s and 0s of digital technology.

But silicon-based microchips are nearing their practical limits, and the semiconductor industry has been investigating new technologies to help chips progress further.

“The traditional integrated circuit is facing some serious problems,” said researcher Peter Dowben at the University of Nebraska-Lincoln. “There is a limit to how much smaller it can get. We’re basically down to the range where we’re talking about 25 or fewer silicon atoms wide. And you generate heat with every device on an (integrated circuit), so you can’t any longer carry away enough heat to make everything work, either.”

“So you need something that you can shrink smaller, if possible. But above all, you need something that works differently than a silicon transistor, so that you can drop the power consumption, a lot.”

So rather than depend on electric charge as the basis of its approach, the team turned to spin: a magnetism-related property of electrons that points up or down and can be read, like electric charge can, as a 1 or 0.

They combined a layer of graphene with chromium oxide which allowed them to flip the spins of the atoms at its surface up or down by applying a small amount of temporary, energy-sipping voltage.

When applying positive voltage, the spins of the underlying chromium oxide point up, ultimately forcing the spin orientation of the graphene’s electric current to veer left and yield a detectable signal in the process.

Negative voltage instead flips the spins of the chromium oxide down, with the spin orientation of the graphene’s current flipping to the right and generating a signal clearly distinguishable from the other.

“Now everybody can get into the game, figuring out how to make the transistor really good and competitive and, indeed, exceed silicon,” Dowben said.

The new, lower power, approach could help to cut the energy footprint of digital memory by 5 per cent globally if widely adopted, the researchers predict.