Optoelectronic synaptic plasticity mimicked in ZnO-based artificial synapse for neuromorphic image sensing application

Memristor-based optoelectronic artificial synapse enables future neuromorphic computing to be more efficient. Hence the development of better optoelectronic artificial synapses becomes considerably important for the era of next-generation neuromorphic computing and neuromorphic visual systems. Optoelectronic artificial synapses can empower neuromorphic visual systems even beyond the visible light region, which has substantial potential to mimic the essential functions of the human visual system. This paper demonstrates a better optoelectronic artificial synapse that shows many fundamental bio-synaptic characteristics. Fabricated devices exhibit excellent paired-pulse facilitation with both electrical and optical input stimuli. The transition from short-term memory to long-term memory was observed for the frequent and high number of input stimuli similar to bio-synapse. Essential Hebbian learning protocols, such as spike-timing-dependent plasticity and spike-rate-dependent plasticity, were successfully emulated in this artificial synapse. It also possesses light-tunable synaptic plasticity, which enables real-time neuromorphic visual pre-processing for realizing neuromorphic visual systems. • Optical paired-pulse facilitation was explored in ITO/ZnO/Ag device. • The ITO/ZnO/Ag device directly responds to both electrical and optical stimuli. • The transition from short term memory to long term memory was observed for both electrical and optical pulse in a single device when a higher number of input stimuli was applied and also for frequent stimulation. • Persistent photoconductivity was observed for a higher number of UV stimuli, which corresponds to the occurrence of long term memory.