Colossal oxygen vacancy formation at a fluorite-bixbyite interface

Dongkyu Lee,Kevin Huang,Ho Nyung Lee,Qiyang Lu,Er-Jia Guo,Lixin Sun,Daniel Haskel,Michael R Fitzsimmons,William T Heller,Matthew F Chisholm,Bilge Yildiz,Youngseok Jee,Thomas O Farmer,Lisha Fan,Yongseong Choi,Xiang Gao,Jonathan Poplawsky

doi:10.1038/s41467-020-15153-8

Abstract

Oxygen vacancies in complex oxides are indispensable for information and energy technologies. There are several means to create oxygen vacancies in bulk materials. However, the use of ionic interfaces to create oxygen vacancies has not been fully explored. Herein, we report an oxide nanobrush architecture designed to create high-density interfacial oxygen vacancies. An atomically well-defined (111) heterointerface between the fluorite CeO2 and the bixbyite Y2O3 is found to induce a charge modulation between Y3+ and Ce4+ ions enabled by the chemical valence mismatch between the two elements. Local structure and chemical analyses, along with theoretical calculations, suggest that more than 10% of oxygen atoms are spontaneously removed without deteriorating the lattice structure. Our fluorite–bixbyite nanobrush provides an excellent platform for the rational design of interfacial oxide architectures to precisely create, control, and transport oxygen vacancies critical for developing ionotronic and memristive devices for advanced energy and neuromorphic computing technologies.

Highlights

Oxygen vacancies in complex oxides are indispensable for information and energy technologies
We investigate the viability of colossal formation of oxygen vacancies in CeO2/Y2O3 superlattices with atomically well-defined (111) interfaces formed within a nanobrush architecture (Fig. 1)
The [(CeO2)[6] u.c./(Y2O3)[2] u.c.]200 nanobrush superlattice was grown by pulsed laser deposition under an extremely nonequilibrium supersaturated condition, which is far away from the conventional condition optimized for the layer-bylayer growth of 2D thin films

Summary

Introduction

Oxygen vacancies in complex oxides are indispensable for information and energy technologies. We report an oxide nanobrush architecture designed to create high-density interfacial oxygen vacancies. Our fluorite–bixbyite nanobrush provides an excellent platform for the rational design of interfacial oxide architectures to precisely create, control, and transport oxygen vacancies critical for developing ionotronic and memristive devices for advanced energy and neuromorphic computing technologies. The bixbyite structure has a “pseudofluorite” structure with an ordered array of vacant oxygen sites occurring on every fourth site (Supplementary Fig. 1), providing an ideal atomic arrangement for forming an interfacial charge layer that originates from the valence mismatch between Ce(4+) and Y(3+). Understanding the details of the interfacial oxygen vacancy formation reported will provide useful insights into developing a novel concept of two-dimensional (2D) ionic channels using atomically engineered oxide interfaces. We investigate the viability of colossal formation of oxygen vacancies in CeO2/Y2O3 superlattices with atomically well-defined (111) interfaces formed within a nanobrush architecture (Fig. 1). The nanobrush superlattices offer many advantages over 2D thin films, including much larger surface areas and a larger number of interfaces than exist in planar films, which are useful for many applications in various technologically relevant areas[22]

Methods

Results

Conclusion