Field Driven Solid-State Defect Control of Bilayer Switching Devices: Ionic Transport Kinetics within Layers and across the Interfaces

Nanoionic devices, crucial for neuromorphic computing and ionically enabled functional actuators, are often kinetically limited. In bilayer configurations, experimentally deconvoluting ion transport within individual layers from the kinetics of transfer across solid-solid interfaces, however, remains a challenge, hindering rational device optimization. Here, we extend the dynamic current-voltage (<i>I</i>-<i>V</i>) technique to a Pr_<i>x</i>Ce_1-<i>x</i>O₂/La_2-<i>x</i>Ce_<i>x</i>CuO₄ (PCO/LCCO) bilayer system, enabling the isolation and quantification of distinct ion transport processes. At high sweep rates, the technique allows quantification of the intralayer transport kinetics within the PCO layer, demonstrating the strong dependence of oxygen vacancy mobility on defect concentration (varying from 2.06 × 10^-12 to 7.31 × 10^-12 cm² V^-1 s^-1 at 50 °C, with activation energies of 0.69-0.86 eV). At lower sweep rates, we identify the kinetic signature of interlayer ion exchange. Arrhenius analysis yields a significantly higher activation energy of 1.03 ± 0.1 eV for this process that we associate with the existence of an interfacial energy barrier, rather than bulk diffusion. This work introduces a methodological framework for studying the transport kinetics of ions in functional bilayers devices, revealing pathways to optimize the speed and performance of such devices.