Fabrication of Freestanding Brownmillerite Strontium Cobalt Oxide Thin Films for Memristive Devices

Abstract

The exploration of artificial synapses is essential for implementing neuromorphic computing to efficiently process large-scale unstructured data. Memristive devices, with characteristics suitable for synaptic plasticity, have been actively studied as artificial synapses. However, ensuring device reliability requires stable control of conductive filaments. In this study, we harnessed the topotactic phase transition (TPT) occurring in the intrinsic oxygen vacancy channels of epitaxially grown brownmillerite SrCoO2.5 (SCO2.5) oriented in the (110) direction. We fabricated a memristive device with an Au/SCO2.5/SrRuO3 (SRO)/SrTiO3 (STO) structure and applied voltage pulses to achieve linear and durable synaptic plasticity through TPT behavior. The TPT behavior was corroborated by density functional theory (DFT) calculations and Raman spectra analysis. Additionally, by introducing a Sr3Al2O6 (SAO) sacrificial layer, we fabricated a heterostructures membrane of SCO2.5/SRO and confirmed the maintained crystallinity through X-ray diffraction (XRD) analysis. Our work provides valuable insights into the fabrication of reliable memristive devices leveraging the TPT behavior in the intrinsic oxygen vacancy channels of SCO2.5 and expanding the scope of their applications.