Abstract
Topotactic phase transition between metallic, perovskite SrFeO3 and insulating, Brownmillerite SrFeO2.5 has been extensively studied due to the potential applications in resistive switching devices for neuromorphic computing. However, its practical utilization as memristors has been hindered by the structural instability of SrFeO3, which is often ascribed to the generation of oxygen vacancies to form SrFeO3-δ. Here we reveal that the dominating defects generated in SrFeO3 epitaxial thin films are atomic scale gaps generated as a result of interfacial strain. Our correlated time- and strain-dependent measurements show that tensile strained SrFeO3 films form vertical, nanoscale gaps that are SrO-rich, which are accountable for the observed metal-to-insulator transition over time. On the other hand, compressively strained or small lattice mismatched SrFeO3 films mainly yield horizontal gaps with a smaller impact on the in-plane transport. The atomic scale origin of such defects and their impact on device performance need to be further understood in order to integrate phase change materials in oxide electronics.
Highlights
Perovskite-structured strontium ferrite SrFeO3, together with its sub stoichiometric oxides SrFeO3-δ (SFO), have attracted great attention due to their rich structural, physical, and chemical properties[1,2,3,4,5,6,7,8,9,10]
While epitaxial growth of SFO in thin film form offers a scalable way to integrate them in oxide electronics, there are still several challenges hindering their practical applications
Bulk SrFeO3 can be readily synthesized through high-pressure and high-temperature techniques, but SFO thin films grown by molecular beam epitaxy (MBE) or pulsed laser deposition (PLD) have been shown to contain significant amount of oxygen vacancies (VOs) due to the low oxygen partial pressure employed[7,12,14,15]
Summary
Perovskite-structured strontium ferrite SrFeO3, together with its sub stoichiometric oxides SrFeO3-δ (SFO), have attracted great attention due to their rich structural, physical, and chemical properties[1,2,3,4,5,6,7,8,9,10]. Conductivity decay over time For the plasma annealed SFO film grown on STO, we tracked its long-term in-plane transport properties as a function of time.
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