Improved synaptic performances with tungsten-doped indium-tin-oxide alloy electrode for tantalum oxide-based resistive random-access memory devices

Abstract

A reliable oxide-based tungsten-doped indium-tin-oxide/tantalum oxide/titanium nitride (W-ITO/TaOx/TiN) memristor with controllable memory states and synaptic properties for neuromorphic computing is proposed herein. Cross-sectional electron energy-dispersive spectroscopy and X-ray photoelectron spectroscopy confirmed alloy W-ITO electrode formation above the TaOx switching layer. Low operation voltage (SET voltage = + 1.2 V and RESET voltage - 1.5 V) with an ON/OFF ratio of > 10 was achieved owing to improved movement of oxygen ions and oxygen vacancies. Resistive-switching cycle-to-cycle variability was improved with a W-doped ITO electrode serving as the oxygen reservoir layer. A gradual step-wise resistance transition during the SET and RESET processes was observed depending on the applied DC step voltages. The conductivity of the synaptic device was successfully controlled by the pulse rise time with a fixed pulse amplitude. Essential synaptic characteristics, namely, spike rate-dependent plasticity, paired-pulse facilitation, and gradual potentiation-depression were implemented in W-ITO/TaOx/TiN memristor. Emulation of synaptic function using the W-doped ITO electrode at the interface and a TaOx-based memristor confirmed the potential for implementation as an artificial synapse.