Investigation of the Switching Mechanism in TiO2 ... - Imperial Spiral

Jul 13, 2016 - FEI Company, P.O. Box 80066, 5600 KA Eindhoven, The Netherlands. §. Department of Chemistry, Imperial College London, Exhibition Road,...
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Investigation of the switching mechanism in TiObased RRAM: a two-dimensional EDX approach Daniela Carta, Iulia Salaoru, Ali Khiat, Anna Regoutz, Christoph Mitterbauer, Nicholas M. Harrison, and Themistoklis Prodromakis ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b04919 • Publication Date (Web): 13 Jul 2016 Downloaded from http://pubs.acs.org on July 16, 2016

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ACS Applied Materials & Interfaces

Investigation of the switching mechanism in TiO2-based RRAM: a two-dimensional EDX approach

Daniela Carta,*,a Iulia Salaoru, a Ali Khiat, a Anna Regoutz, a Christoph Mitterbauer, b Nicholas M. Harrison, c Themistoklis Prodromakis a

a

Nano Group, Southampton Nanofabrication Centre, Department of Electronics and Computer

Science, University of Southampton, Southampton SO17 1BJ, United Kingdom b

FEI Company, P.O. Box 80066, 5600 KA Eindhoven, The Netherlands

c

Department of Chemistry, Imperial College London, Exhibition Road, London SW7 2AZ, United

Kingdom

*

Corresponding Author. E-mail: [email protected]

Keywords: resistive memory, titanium dioxide, memristors, energy dispersive X-ray spectroscopy, thin films, resistive switching 1 ACS Paragon Plus Environment

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Abstract The next generation of non-volatile memory storage may well be based on resistive switching in metal oxides. TiO2 as transition metal oxide has been widely used as active layer for the fabrication of a variety of multi-state memory nanostructure devices. However, progress in their technological development has been inhibited by the lack of a thorough understanding of the underlying switching mechanisms. Here, we employed high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) combined with two-dimensional energy dispersive X-ray spectroscopy (2D EDX) to provide a novel, nanoscale view of the mechanisms involved. Our results suggest that the switching mechanism involves redistribution of both Ti and O ions within the active layer combined with an overall loss of oxygen that effectively render conductive filaments. Our study shows evidence of titanium movement in a 10 nm TiO2 thin-film through direct EDX mapping that provides a viable starting point for the improvement of the robustness and life time of TiO2-based resistive random access memory (RRAM).

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1.

Introduction

Nanoscale resistive random access memory (RRAM) cells are typically metal-insulator-metal (MIM) architectures where the insulator typically comprises a transition metal oxide thin-film. RRAM cells are also known as memristors and due to their simple structure can be incorporated into devices with high density that function at low power and high speed (