Synaptic plasticity in Co/Nb:STO memristive devices: The role of oxygen vacancies

TL;DR

This paper demonstrates that oxygen vacancy electromigration in Co/Nb:STO memristors enables both short-term and long-term synaptic plasticity, advancing neuromorphic device development.

Contribution

It reveals the role of oxygen vacancies in controlling synaptic plasticity types in Co/Nb:STO memristors, supported by experimental and modeling insights.

Findings

Resistance follows a power-law during short-term plasticity

Successive pulses induce stepwise resistance increase for long-term memory

Oxygen vacancy distribution modulates the Schottky barrier

Abstract

Neuromorphic computing aims to develop energy-efficient devices that mimic biological synapses. One promising approach involves memristive devices that can dynamically adjust their electrical resistance in response to stimuli, similar to synaptic weight changes in the brain. However, a key challenge is understanding and controlling the coexistence of different types of synaptic plasticity, such as short-term and long-term plasticity. In this work, we show that plasticity behaviors in Co/Nb:STO Schottky memristors originate from oxygen vacancy electromigration, which modulates the Schottky barrier and enables both short-term and long-term plasticity. Our experiments reveal that resistance changes follow a power-law during reading (short-term plasticity) and increase stepwise with successive pulses (long-term memory retention). These behaviors are successfully reproduced by our model, which demonstrates the correlation between oxygen vacancy distribution and Schottky barrier modulation. Our findings highlight these memristors as promising candidates for neuromorphic applications.