To date, memristors have been two terminal electronic devices, which can only control one voltage channel. However, Mark Hersam, from the University's McCormick School of Engineering, wanted to create a three terminal device that could be used in more complex electronic circuits and systems.
Hersam and his team used single layer molybdenum disulphide (MoS2) in their work. The sheet of MoS2 used by Hersam has a well defined grain boundary; 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 said. "These grain boundaries influence the flow of current, so they can serve as a means of tuning resistance."
According to the team, when a large electric field is applied, the grain boundary moves, causing a change in resistance. By using MoS2, instead of the metal-oxide-metal structure found in a typical memristor, the team created a 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 and we are actively exploring this possibility in the laboratory."