Forming-free bipolar resistive switching in nonstoichiometric ceria films

Muhammad Ismail,Debashis Panda,Ijaz Talib,Jheng-Hong Jieng,Anwar Manzoor Rana,Ejaz Ahmed,Umesh Chand,Tsung-Ling Tsai,Chung-Jung Hung,Muhammad Younus Nadeem,Chun-Yang Huang,Tseung-Yuen Tseng,Chun-An Lin

doi:10.1186/1556-276x-9-45

Abstract

The mechanism of forming-free bipolar resistive switching in a Zr/CeO x /Pt device was investigated. High-resolution transmission electron microscopy and energy-dispersive spectroscopy analysis indicated the formation of a ZrO y layer at the Zr/CeO x interface. X-ray diffraction studies of CeO x films revealed that they consist of nano-polycrystals embedded in a disordered lattice. The observed resistive switching was suggested to be linked with the formation and rupture of conductive filaments constituted by oxygen vacancies in the CeO x film and in the nonstoichiometric ZrO y interfacial layer. X-ray photoelectron spectroscopy study confirmed the presence of oxygen vacancies in both of the said regions. In the low-resistance ON state, the electrical conduction was found to be of ohmic nature, while the high-resistance OFF state was governed by trap-controlled space charge-limited mechanism. The stable resistive switching behavior and long retention times with an acceptable resistance ratio enable the device for its application in future nonvolatile resistive random access memory (RRAM).

Highlights

A metal-insulator-metal (MIM) structure-based resistive random access memory (RRAM) device has attracted much attention for next-generation high-density and low-cost nonvolatile memory applications due to its long data retention, simple structure, high-density integration, low-power consumption, fast operation speed, high scalability, simple constituents, and easy integration with the standard metal oxide semiconductor (MOS) technology [1]
We have found that the CeOx-based RRAM device exhibits good switching characteristics with reliable endurance and data retention, suitable for future nonvolatile memory applications
From the X-ray diffraction (XRD) analysis, the broad and wide diffraction peaks demonstrate that the CeOx film exhibits poor crystallization

Summary

Introduction

A metal-insulator-metal (MIM) structure-based resistive random access memory (RRAM) device has attracted much attention for next-generation high-density and low-cost nonvolatile memory applications due to its long data retention, simple structure, high-density integration, low-power consumption, fast operation speed, high scalability, simple constituents, and easy integration with the standard metal oxide semiconductor (MOS) technology [1]. In addition to transition metal oxide-based RRAMs [2,3], many rare-earth metal oxides, such as Lu2O3, Yb2O3, Sm2O3, Gd2O3, Tm2O3, Er2O3, Nd2O3, Dy2O3, and CeO2 [4,5,6,7,8,9,10], show very good resistive switching (RS) properties. It is expected that the Zr top electrode reacts with the CeOx layer and forms an interfacial ZrOy layer. This reaction may be responsible for creating a sufficient amount of oxygen vacancies required for the formation and rupture of conductive filaments for resistive switching. We have found that the CeOx-based RRAM device exhibits good switching characteristics with reliable endurance and data retention, suitable for future nonvolatile memory applications

Methods

Results

Conclusion