SUPERMEM explores memristors, which are a new class of electronic memory devices. Their functionality is beyond that of conventional (binary) memories: they show a continuum of states (instead of just two), and the switching is driven by the “history” of stimuli (e.g. a sequence of voltage pulses). Thus, memristors can be thought of as multi-state memories switchable by cumulative stimuli. Because they can mimic the function of synapses in the brain, memristors are key in the nascent field of neuromorphic computing, and they stay in the spotlight of industrials for creating a leap in information technologies.
The particularity of the project is that we have explored memristors based on strongly correlated transition metal oxides, a family of materials that includes high-temperature superconducting cuprates. Our devices exploit a physical mechanism we demonstrated earlier in the framework of the ERC project SUSPINTRONICS, namely, a reversible redox reaction occurring at the interface between the strongly correlated oxide and a metal with low reduction potential. This electrochemical reaction produces an oxygen exchange between both materials, which changes their interfacial and determines the electrical resistance across the interface. The reaction can be driven and reversed by applying voltage pulses of different polarity (very much as a battery can be charged and discharged), yielding different non-volatile resistance states. Despite their structural simplicity -the device is just an interface- these memristors replicate the functionalities of much more complex schemes.
With SUPERMEM, we have characterized and optimized some crucial aspects of those new redox memristors. We have optimized their resistance switching amplitude by investigating different materials combinations (including new oxide and metallic compounds), characterized the dynamic properties (switching speed, relaxation, endurance, retention), as well as demonstrated that the switching between different resistive states can be triggered optically -thus creating a novel photo-memristor function. We have already published some of these results recently. One device that exploits those effects has been invented (patent filed and published) and two other pates are under preparation currently.
