Electrode Oxygen Exchange Enables Polarity‐Controlled Resistive Switching in Topotactic SrCoO 2.5

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Abstract
Resistive switching in SrCoO 2.5 has been variably attributed to localized filamentary conduction and lattice‐scale oxygen redox; as a topotactic oxide capable of reversible oxygen exchange with minimal lattice disruption, it provides a model system to resolve this distinction, which is critical because the underlying mechanism governs switching stability, reproducibility, and device design. Here, we address this issue by directly comparing Au/SrCoO 2.5 /Nb‐SrTiO 3 and SrRuO 3 /SrCoO 2.5 /Nb‐SrTiO 3 heterostructures using electrical transport measurements combined with operando bias‐dependent x‐ray absorption and hard x‐ray photoelectron spectroscopy, providing direct sensitivity to lattice‐oxygen‐driven redox processes. Devices with an oxygen‐inert Au electrode exhibit polarity‐restricted switching, whereas the oxygen‐active SrRuO 3 electrode exhibits switching under both bias polarities within the investigated voltage window, consistent with participation of both interfaces in the bias‐induced redox response. Operando spectroscopy reveals electrode‐dependent modulation of the Co valence, while complementary structural and vibrational measurements show no macroscopic lattice change but clear local rearrangements of the oxygen coordination, indicating an interface‐controlled, spatially distributed redox mechanism. These results identify electrode oxygen‐exchange capability as an important parameter governing switching polarity and redox dynamics in topotactic transition‐metal oxides. The combined electrical and spectroscopic observations further support the contribution of a distributed redox mechanism to the switching process.
Funding Information
  • Anusandhan National Research Foundation (EEQ/2023/000089)

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