Reversible ionic transfer between two solid metal oxides controlled by E-field

How can applied voltage be used to control solid-state oxygen ion exchange?

Thomas Defferriere, Frances Ross, Harry Tuller, and their colleagues at the Massachusetts Institute of Technology published on their use of the Hummingbird Scientific in-situ MEMS heating + biasing TEM holder to examine electric field-driven solid-state control of oxygen ion transfer between two solid metal oxides in bilayer switching devices. The reversible transport of oxygen ions at ambient temperature using applied voltage enabled determination of defect concentrations and the impact on film conductance.

a) Schematic of field driven solid-state defect chemical-controlled bilayer switching device. Systematic variation in bias polarity and magnitude leads to controllable exchange of ions between the two metal oxide layers, subsequently correlated with device property changes. b) Top view light microscope image of the device with contacts showing the two crossed ITO electrodes (gray) that sandwich the PCO/LCCO stack (orange). c) Cross-sectional TEM image of an ITO/PCO/LCCO/ITO device grown on Nb-doped SrTiO₃ substrate. d-f) Fast Fourier transforms (FFT) of three adjacent grains in the LCCO layer, as highlighted by the colored border frames in (c). g) FFT of the entire ITO/PCO/LCCO/ITO layer as highlighted by the dotted red frame in (c). Copyright © 2024 American Chemical Society

Scanning transmission electron microscopy (STEM) imaging and electron energy loss spectroscopy (EELS) analysis techniques captured reversible structural and chemical changes during modulation of the bilayer device via DC potentiostatic measurements. Electrochemical impedance spectroscopy measurements as a function of temperature were employed to distinguish contributions of each layer to the total device resistance. Conductance changes for each layer followed the expected trends for oxygen activity-dependent conductance previously studied at elevated temperatures. The technique and findings will enable optimization of materials selection and determination of design criteria for applied bilayer systems.

Reference: Thomas Defferriere, Baoming Wang, Julian Klein, Frances M. Ross, and Harry L. Tuller, Advanced Materials & Interfaces XX (X) XXX-XXX (2024) DOI: 10.1021/acsami.4c09826

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