Using a mixed ionic electronic conductor to build an analog memristive device with neuromorphic programming capabilities

Interface-type oxide-based valence-change memories (VCMs) with analog switching capabilities and memory transience are interesting candidates to be used as artificial synapses for the hardware implementation of artificial neural networks (ANNs) with short-term synaptic dynamics. Here, the mixed ionic-electronic conducting (MIEC) oxide La2NiO4+delta (L2NO4) is used to rationally design a new volatile interfacetype valence-change memory based on a tunable p-n junction between a p-type MIEC oxide and an n-type "oxygen-reservoir'' oxide. The memory does not require a forming step to trigger memristance and exhibits a highly multilevel and bipolar analogtype change in resistance, which can be continuously varied by over two orders of magnitude. A distinctive two-step memory transience where the resistance of the unbiased device increases before relaxing back to a lower resistance state was measured and has been attributed to the Fick diffusion of oxygen ions, restoring the drift-induced concentration gradients at the Ti/L2NO4 interface.