Artificial synapse characteristics of a ZnO-based memristor with a short-term memory effect

We fabricated and characterized a Ni/ZnO/TiN memristor device designed to emulate an artificial synapse for use in a neuromorphic system. Chemical and material characterization was conducted using ultraviolet photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy. The device exhibited gradual resistive switching as a multi-level cell with an increase in the DC sweep voltage. Current decay was observed after the set process, indicating that it could feasibly be employed in short-term memory applications. We demonstrated both short-term memory and long-term memory behavior in the proposed device. Higher conductance was maintained via repetitive pulses with a high voltage and a short time interval, while conductance was lower when repetitive pulses with a low voltage and a short time interval were employed. Pulse interval-dependent paired-pulse facilitation characteristics were used to mimic an artificial synapse, with potentiation and depression observed over multiple cycles. We also evaluated the pattern-recognition accuracy of the proposed conductance modulation with degradation based on the short-term memory effect using a 784 x 10 cross-point array netlist and a SPICE resistor model.