Ion-Gel-Gating-Induced Oxygen Vacancy Formation in Epitaxial La0.5Srd0.5^CoO^d3-δ Films from in operando X-ray and Neutron Scattering

Published

December 19, 2017

Author(s)

Jeff Walter, Guichuan Yu, Biqiong Yu, Alexander Grutter, Brian Kirby, Julie Borchers, Zhan Zhang, Hua Zhou, Turan Birol, Martin Greven, Chris Leighton

Abstract

Ionic-liquid/gel-based transistors have emerged as an ideal means to accumulate high charge carrier densities at the surfaces of materials such as oxides, enabling control over electronic phase transitions. Substantial gaps remain in the understanding of the active gating mechanisms however, particularly with respect to charge carrier vs. oxygen defect creation, one contributing factor being the death of experimental probes beyond transport. Here we demonstrate the use of synchrotron hard X-ray diffraction and polarized neutron reflectometry as in operando probes of ion-gel transistors based on ferromagnetic La_0.5Sr_0.5CoO^d3-δ. An asymmetric gate bias response is confirmed to derive from electrostatic hole accumulation at negative gate bias vs. oxygen vacancy formation at positive bias. The latter is detected Ivia a large (up to 1 %) gate-induced lattice expansion, complementary bulk measurements and density functional calculations enabling quantification of the bias-dependent oxygen vacancy density. Remarkably, the gate-induced oxygen vacancies proliferate through the entire thickness of 30-40-unit-cell-thick films, quantitatively accounting for subsequent changes in the magnetization depth profile. These results directly elucidate the issue of electrostatic vs. redox-based response in electrolyte-gated oxides, also establishing powerful new approaches to their in operando investifation.

Citation

Physical Review Materials

Volume

1

Issue

7

Pub Type

Journals

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Keywords

magnetism

Citation

Walter, J. , Yu, G. , Yu, B. , Grutter, A. , Kirby, B. , Borchers, J. , Zhang, Z. , Zhou, H. , Birol, T. , Greven, M. and Leighton, C. (2017), Ion-Gel-Gating-Induced Oxygen Vacancy Formation in Epitaxial La_0.5Srd0.5^CoO^d3-δ Films from in operando X-ray and Neutron Scattering, Physical Review Materials, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=924847 (Accessed December 5, 2024)