Oxygen vacancy engineering of TaOx-based resistive memories by Zr doping for improved variability and synaptic behavior

TL;DR

This study demonstrates that Zr doping in TaOx resistive memory devices reduces device variability and enhances synaptic-like switching behavior by controlling oxygen vacancy formation and filament localization.

Contribution

The paper introduces Zr doping as a novel method to control oxygen vacancies in TaOx-based resistive memories, significantly improving device consistency and synaptic performance.

Findings

Device-to-device variability reduced by a factor of 7

Resistance window doubled in Zr-doped devices

Achieved more gradual and monotonic LTP/LTD switching

Abstract

Resistive switching devices are promising emerging non-volatile memories. However, one of the biggest challenges for resistive switching (RS) memory applications is the device-to-device (D2D) variability which is related to the intrinsic stochastic formation and configuration of oxygen vacancy (VO) conductive filaments. In order to reduce D2D variability, the control of oxygen vacancy formation and configuration is paramount. We report in this study Zr doping of TaOx-based RS devices prepared by pulsed laser deposition (PLD) as an efficient mean to reduce VO formation energy and increase conductive filament (CF) confinement, thus reducing D2D variability. Such findings were supported by X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE) and electronic transport analysis. Zr doped films presented increased VO concentration, and more localized VO thanks to the interaction with Zr. According to DC and pulse mode electrical characterization, D2D variability was decreased by a factor of 7, resistance window was doubled and a more gradual and monotonic long-term potentiation/depression (LTP/LTD) in pulse switching was achieved in forming-free Zr:TaOx devices thus displaying promising performance for artificial synapse applications.