Enhanced Synaptic Features of ZnO/TaOx Bilayer Invisible Memristor for Brain-Inspired Computing

In this letter, we present a transparent bilayer ZnO/TaOx memristive synapse for brain-inspired computing. The device shows excellent AC endurance (<inline-formula> <tex-math notation="LaTeX">$10^{{9}}$ </tex-math></inline-formula> cycles) and high-temperature retention (<inline-formula> <tex-math notation="LaTeX">$10^{{4}}$ </tex-math></inline-formula> s) without any degradation at 100 °C. The device exhibits highly stable repetitive 5130 potentiation (P) and depression (D) epochs with 1.026 M pulses. The multilevel characteristics (MLC) of the device are achieved by changing the pulse height from 0.7 to 1.1 V for long-term potentiation (LTP) and from −0.9 to −1.3 V for long-term depression (LTD) having gradual conductance change for both P and D cases. The synaptic features such as paired-pulse facilitation (PPF) and spike time-dependent plasticity (STDP) are measured using consecutive AC pulses. These unique features confirm that the synaptic device has excellent capability for the application in the brain-inspired computing systems.