2 min readNew Material Created that Could Allow Computers to Mimic the Human Brain

Evanston, IL — Researchers from Northwestern University have made a step forward in memristor technology that could bring us closer to brain-like computing.

For decades, academic and industrial laboratories have been working to create computers that could operate more like the human brain. The most efficient of computers, it has nearly limitless memory, is difficult to crash, and works at extremely fast speeds. No wonder that engineers and scientists around the world want to mimic its abilities.

A team of Northwestern researchers has accomplished a new step forward in electronics that could bring brain-like computing closer to reality. The team’s work advances memory resistors, or “memristors,” which are resistors in a circuit that “remember” how much electrical current has flowed through them. The research is described in the April 6 issue of Nature Nanotechnology.

“Memristors could be used as a memory element in an integrated circuit or computer,” said one of the project’s co-advisors, Mark Hersam, from Northwestern University’s McCormick School of Engineering. “Unlike other memories that exist today in modern electronics, memristors are stable and remember their state even if you lose power.”

Current computers use random access memory (RAM), which moves very quickly as a user works but does not retain unsaved data if power is lost. Flash drives, on the other hand, store information when they are not powered but work much slower. Memristors could provide a memory that is the best of both worlds: fast and reliable. But there’s a problem: memristors are two-terminal electronic devices, which can only control one voltage channel. Hersam wanted to transform it into a three-terminal device, allowing it to be used in more complex electronic circuits and systems.

Hersam and his team met this challenge by using single-layer molybdenum disulfide (MoS2), an atomically thin, two-dimensional nanomaterial semiconductor. Much like the way fibers are arranged in wood, atoms are arranged in a certain direction–called “grains”–within a material. The sheet of MoS2 that Hersam used has a well-defined grain boundary, which is the interface where two different grains come together.

“Because the atoms are not in the same orientation, there are unsatisfied chemical bonds at that interface,” Hersam explained. “These grain boundaries influence the flow of current, so they can serve as a means of tuning resistance.”

When a large electric field is applied, the grain boundary literally moves, causing a change in resistance. By using MoS2 with this grain boundary defect instead of the typical metal-oxide-metal memristor structure, the team presented a novel three-terminal memristive device that is widely tunable with a gate electrode.

“With a memristor that can be tuned with a third electrode, we have the possibility to realize a function you could not previously achieve,” Hersam said. “A three-terminal memristor has been proposed as a means of realizing brain-like computing. We are now actively exploring this possibility in the laboratory.”

Article adapted from a Northwestern University news release.

 Publication: Gate-tunable memristive phenomena mediated by grain boundaries in single-layer MoS2. Sangwan V  et al. Nature Nanotechnology (April 6, 2015): Click here to view.

Brain, Nanoengineering, Nanotechnology

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