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Epitaxial heterostructures of iron oxide thin films on oxide substrates have broad prospects in spintronics applications. Reducing such heterostructures to ordered nanostructures allows integration into functional devices. However, fabricating ordered nanostructures while maintaining their structural and functional integrity remains challenging. A bottom-up approach is used to grow epitaxial Fe3O4 nanoarrays on Nb-doped SrTiO3 (Nb:STO) substrates, integrating anodic aluminum oxide (AAO) templates with pulsed laser deposition.Using this method, the lateral confinement of Fe3O4 was then confirmed through grazing incidence small-angle X-ray scattering (GISAXS) and scanning electron microscopy (SEM), showing that the nanodots possess 3D long-range order, with sizes of 30 and 70 nm. Based on this structural evidence, it was found that the Verwey transition is preserved, as observed in continuous films. To explore its applicability in nanoelectronics, conductive atomic force microscopy (c-AFM) was used to probe local electrical behavior, revealing bipolar resistive switching of individual nanodots at room temperature, consistent with the behavior observed in films. In summary, these results demonstrate for the first time that ordered epitaxial Fe3O4/Nb:STO nanodots retain structural, magnetic, and electrical functionality, providing a general route for nanoscale integration of complex oxides.
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A study in Advanced Materials demonstrated high-quality Fe₃O₄ nanodot arrays (30/70 nm) on Nb-doped SrTiO₃ substrates via bottom-up AAO templating and PLD. These nanodots retained hexagonal order (confirmed by GISAXS/SEM), crystallinity, and the Verwey transition, with a ~3 nm γ-Fe₂O₃ interfacial layer revealed by polarized neutron reflectometry. Electrical tests showed stable bipolar resistive switching in 30 nm dots, likely linked to oxygen exchange at the γ-Fe₂O₃ layer, highlighting their potential for high-density storage and spintronic devices.
References:
DOI: 10.1002/adma.202517938
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