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Title: Ion-gel-gating-induced oxygen vacancy formation in epitaxial L a 0.5 S r 0.5 Co O 3 δ films from in operando x-ray and neutron scattering

Abstract

Ionic-liquid/gel-based transistors have emerged as a potentially 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 gating mechanisms, however, particularly with respect to charge carrier vs oxygen defect creation, one contributing factor being the dearth of experimental probes beyond electronic 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 3-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 via a large gate-induced lattice expansion (up to 1%), 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 changes in the magnetization depth profile. In conclusion, these results directly elucidate the issue of electrostatic vs redox-based response in electrolyte-gated oxides, also demonstrating powerful approaches to their in operando investigation.

Authors:
 [1];  [1];  [1];  [2];  [2];  [2];  [3];  [3];  [1];  [1];  [1]
  1. Univ. of Minnesota, Minneapolis, MN (United States)
  2. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States)
  3. Argonne National Lab. (ANL), Argonne, IL (United States)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
National Science Foundation (NSF); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1466375
Alternate Identifier(s):
OSTI ID: 1414041
Grant/Contract Number:  
AC02-06CH11357; FG02-06ER46275; SC0016371
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physical Review Materials
Additional Journal Information:
Journal Volume: 1; Journal Issue: 7; Journal ID: ISSN 2475-9953
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Walter, Jeff, Yu, Guichuan, Yu, Biqiong, Grutter, Alexander, Kirby, Brian, Borchers, Julie, Zhang, Zhan, Zhou, Hua, Birol, Turan, Greven, Martin, and Leighton, Chris. Ion-gel-gating-induced oxygen vacancy formation in epitaxial La0.5Sr0.5CoO3–δ films from in operando x-ray and neutron scattering. United States: N. p., 2017. Web. doi:10.1103/PhysRevMaterials.1.071403.
Walter, Jeff, Yu, Guichuan, Yu, Biqiong, Grutter, Alexander, Kirby, Brian, Borchers, Julie, Zhang, Zhan, Zhou, Hua, Birol, Turan, Greven, Martin, & Leighton, Chris. Ion-gel-gating-induced oxygen vacancy formation in epitaxial La0.5Sr0.5CoO3–δ films from in operando x-ray and neutron scattering. United States. doi:10.1103/PhysRevMaterials.1.071403.
Walter, Jeff, Yu, Guichuan, Yu, Biqiong, Grutter, Alexander, Kirby, Brian, Borchers, Julie, Zhang, Zhan, Zhou, Hua, Birol, Turan, Greven, Martin, and Leighton, Chris. Tue . "Ion-gel-gating-induced oxygen vacancy formation in epitaxial La0.5Sr0.5CoO3–δ films from in operando x-ray and neutron scattering". United States. doi:10.1103/PhysRevMaterials.1.071403. https://www.osti.gov/servlets/purl/1466375.
@article{osti_1466375,
title = {Ion-gel-gating-induced oxygen vacancy formation in epitaxial La0.5Sr0.5CoO3–δ films from in operando x-ray and neutron scattering},
author = {Walter, Jeff and Yu, Guichuan and Yu, Biqiong and Grutter, Alexander and Kirby, Brian and Borchers, Julie and Zhang, Zhan and Zhou, Hua and Birol, Turan and Greven, Martin and Leighton, Chris},
abstractNote = {Ionic-liquid/gel-based transistors have emerged as a potentially 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 gating mechanisms, however, particularly with respect to charge carrier vs oxygen defect creation, one contributing factor being the dearth of experimental probes beyond electronic 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 La0.5Sr0.5CoO3-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 via a large gate-induced lattice expansion (up to 1%), 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 changes in the magnetization depth profile. In conclusion, these results directly elucidate the issue of electrostatic vs redox-based response in electrolyte-gated oxides, also demonstrating powerful approaches to their in operando investigation.},
doi = {10.1103/PhysRevMaterials.1.071403},
journal = {Physical Review Materials},
issn = {2475-9953},
number = 7,
volume = 1,
place = {United States},
year = {2017},
month = {12}
}

Journal Article:
Free Publicly Available Full Text
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Cited by: 11 works
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Figures / Tables:

Fig. 1 Fig. 1: (more » a) Device and experimental setup schematic for synchrotron x-ray diffraction on epitaxial La0.5Sr0.5CoO3δ films. (b) Gate-bias-(Vg)-dependent specular diffraction (00L) scans, where L is in reciprocal lattice units (r.l.u.) of the LAO substrate. (c) Change in c-axis lattice parameter (Δcop, left axis) and cell volume (ΔV, right axis) with Vg. (d) Change in Scherrer thickness (Δts, left axis), and ts itself (right axis), vs Vg. (e) Change in film thickness from Laue fringes (Δtf), and tf itself (right axis), vs Vg. Blue dotted lines are guides to the eye.« less

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    Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.