Artificial synaptic characteristics with strong analog memristive switching in a Pt/CeO/Pt structure.

Artificial synaptic potentiation and depression characteristics were demonstrated with Pt/CeO/Pt devices exhibiting polarity-dependent analog memristive switching. The strong and sequential resistance change with its maximum to minimum ratio >10, imperatively essential for stable operation, as repeating voltage application, emulated the potentiation and depression motion of a synapse with variable synaptic weight. The synaptic weight change could be controlled by the amplitude, width, and number of repeated voltage pulses. The voltage polarity-dependent and asymmetric current-voltage characteristics and consequential resistance change are thought to be due to local inhomogeneity of electrical and physical states of CeO such as charging at interface states, valence changes of Ce cations, and so on. These results revealed that the CeO layer could be a promising material for analog memristive switching elements with strong resistance change, as an artificial synapse in neuromorphic systems.