US researchers use MoS2 for three-terminal memristor
A team of researchers from Northwestern University, Illinois, has used single-layer MoS2, an atomically thin, 2D compound semiconductor, to bring brain-like computing closer to reality.
The team's work advances 'memristors' which are resistors in a circuit that 'remember' how much 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 Mark Hersam, the Bette and Neison Harris Chair in Teaching Excellence in 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."
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.
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 realise a function you could not previously achieve," Hersam said. "A three-terminal memristor has been proposed as a means of realising brain-like computing. We are now actively exploring this possibility in the laboratory."
"Computers are very impressive in many ways, but they're not equal to the mind," he said. "Neurons can achieve very complicated computation with very low power consumption compared to a digital computer."
'Gate-tunable memristive phenomena mediated by grain boundaries in single-layer MoS2' by Vinod K Sangwan et al, Nature Nanotechnology (2015) doi:10.1038/nnano.2015.56
