Confining vertical conducting filament for reliable resistive switching by using a Au-probe tip as the top electrode for epitaxial brownmillerite oxide memristive device

Venkata Raveendra Nallagatla,Miyoung Kim,Janghyun Jo,Susant Kumar Acharya,Chang Uk Jung

doi:10.1038/s41598-018-37986-6

Venkata Raveendra Nallagatla, Miyoung Kim + Show 3 more

Open Access

https://doi.org/10.1038/s41598-018-37986-6

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Abstract

We had discovered novel resistance switching phenomena in SrCoOx epitaxial thin films. We have interpreted the results in terms of the topotactic phase transformation between their insulating brownmillerite phase and the conducting perovskite phase and the existence of a rather vertical conducting filament due to its inherent layered structure. However, the rough interface observed between the SrCoOx and the Au top electrode (area ~10000 μm2) was assumed to result in the observed fluctuation in key switching parameters. In order to verify the effect of rough interface on the switching performance in the SrCoOx device, in this work, we studied the resistive switching properties of a SrCoOx device by placing a Au-coated tip (end area ~0.5 μm2) directly on the film surface as the top electrode. The resulting device displayed much improved endurance and showed high uniformity in key switching parameters as compared to the device having a large top electrode area. A simulation result confirmed that the Au-coated tip provides a local confinement of the electrical field, resulting in confinement of oxygen ion distribution and therefore localization of the conducting filament. By minimizing other free and uncontrollable parameters, the designed experiment here provides the most direct and isolated evidence that the rough interface between electrode and ReRAM matrix is detrimental for the reproducibility of resistivity switching phenomena.

Highlights

Resistive random access memory (ReRAM) with a simple metal-insulator-metal structure shows promising characteristics in terms of scalability, low power operation, and multilevel data storage capability, and it is suitable for next-generation memory applications[1,2,3]
It has been reported that increasing the roughness at the metal/oxide interface can decrease the variability in the switching parameters of a ReRAM device including set and reset voltages and high-resistance states (HRS) and low-resistance states (LRS) resistances[20]
The probe tip-based devices show good resistive switching (RS) properties including stable endurance and retention compared to devices based on a large electrode area

Summary

Introduction

Resistive random access memory (ReRAM) with a simple metal-insulator-metal structure shows promising characteristics in terms of scalability, low power operation, and multilevel data storage capability, and it is suitable for next-generation memory applications[1,2,3]. These methods include the insertion of metal nanodots or nanoparticles[14], employing a nanovia electrode structure[16] and geometrically embedding nanotip electrodes[11] All these methods have been used to control the O2− ions or vacancies generation rate and distribution, so that the CF was confined along the same path as the preferential sites. We observed the RS behavior in Au(100 μm)/SrFeOx/SRO in which SrFeOx thin film was grown with an atomically smooth surface[26] This SrFeOx thin film device exhibited better reproducible switching behavior with narrow distribution of the switching characteristics even in a large TE area (100 μm × 100 μm), due to the reduced probability of random generation of CFs

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