Endurance and Cycle-to-cycle Uniformity Improvement in Tri-Layered CeO2/Ti/CeO2 Resistive Switching Devices by Changing Top Electrode Material

Anwar Manzoor Rana,Muhammad Imran,Fayyaz Hussain,Ijaz Talib,Khalid Iqbal,Khalid Mehmood,Tahira Akbar,Muhammad Ismail,Ejaz Ahmad,M Younus Nadeem

doi:10.1038/srep39539

Abstract

Resistance switching characteristics of CeO2/Ti/CeO2 tri-layered films sandwiched between Pt bottom electrode and two different top electrodes (Ti and TaN) with different work functions have been investigated. RRAM memory cells composed of TaN/CeO2/Ti/CeO2/Pt reveal better resistive switching performance instead of Ti/CeO2/Ti/CeO2/Pt memory stacks. As compared to the Ti/CeO2 interface, much better ability of TaN/CeO2 interface to store and exchange plays a key role in the RS performance improvement, including lower forming/SET voltages, large memory window (~102) and no significant data degradation during endurance test of >104 switching cycles. The formation of TaON thinner interfacial layer between TaN TE and CeO2 film is found to be accountable for improved resistance switching behavior. Partial charge density of states is analyzed using density functional theory. It is found that the conductive filaments formed in CeO2 based devices is assisted by interstitial Ti dopant. Better stability and reproducibility in cycle-to-cycle (C2C) resistance distribution and Vset/Vreset uniformity were achieved due to the modulation of current conduction mechanism from Ohmic in low field region to Schottky emission in high field region.

Highlights

The proposed resistive memory devices were fabricated as follows: A 20-nm-thick adhesion layer of Ti and a 70-nm-thick Pt film were deposited as the bottom electrode on a SiO2/p-Si (100) substrate using e-beam evaporation
An ultra-thin Ti (~1 nm) layer was deposited on CeO2/Pt using Ti metal target by radio frequency (RF) magnetron sputtering with 60 W power
The three sequential layers CeO2/Ti/CeO2 were deposited by RF magnetron sputtering

Summary

Introduction

The proposed resistive memory devices were fabricated as follows: A 20-nm-thick adhesion layer of Ti and a 70-nm-thick Pt film were deposited as the bottom electrode on a SiO2/p-Si (100) substrate using e-beam evaporation. First layer of CeO2 (6 nm) was deposited on Pt bottom electrode. An ultra-thin Ti (~1 nm) layer was deposited on CeO2/Pt using Ti metal target by radio frequency (RF) magnetron sputtering with 60 W power. The working pressure was maintained at 10 mTorr using 20 sccm argon gas flow.

Results

Conclusion