# From Thin Films to Nanodots: Bottom‐Up Integration of Fe3O4 on Nb:STO for Functional Oxide Nanostructures

## TL;DR

Researchers developed a method to create ordered Fe3O4 nanodots on a substrate, preserving their structural and functional properties for potential use in nanoelectronics.

## Contribution

First demonstration of ordered epitaxial Fe3O4/Nb:STO nanodots with preserved structural, magnetic, and electrical functionalities.

## Key findings

- Fe3O4 nanodots with 30 and 70 nm diameters show 3D long-range ordering confirmed by GISAXS and SEM.
- Nanodots retain the Verwey transition and exhibit bipolar resistive switching at room temperature.
- Ordered arrays of nanodots maintain crystallographic and magnetic properties of continuous films.

## Abstract

Epitaxial heterostructures of iron oxide thin films on oxide substrates are promising for spintronic applications. Scaling down such heterostructures into ordered nanostructures enables integration into functional devices. However, fabricating well‐ordered nanostructures while retaining their structural and functional integrity remains challenging. A bottom‐up approach is used to grow epitaxial Fe3O4 nanodot arrays on Nb‐doped SrTiO3(Nb:STO) substrates integrating anodic aluminum oxide (AAO) templates combined with pulsed laser deposition. Following this method, the lateral confinement of Fe3O4 into 30 and 70 nm nanodots with 3D long‐range ordering is then confirmed by grazing‐incidence small‐angle X‐ray scattering (GISAXS) and scanning electron microscopy (SEM). Building on this structural evidence, the Verwey transition is found to be retained, as observed in the continuous film. To explore its applicability in nanoelectronics, conductive atomic force microscopy (c‐AFM) is used to probe local electrical behavior, and reveals bipolar resistive switching at room temperature in individual nanodots, consistent with behavior observed in thin films. Together, these results establish the first demonstration of ordered epitaxial Fe3O4/Nb:STO nanodots with preserved structural, magnetic, and electrical functionalities, providing a generalizable route for nanoscale integration of complex oxides.

Scalable bottom‐up fabrication of Fe3O4 nanodots on Nb:SrTiO3 using anodic alumina templates enables long‐range ordered arrays with diameters down to 30 nm. STEM highlights the epitaxial growth of Fe3O4 films on Nb:SrTiO3. Complementary polarized neutron reflectometry (PNR) and X‐ray magnetic circular dichroism (XMCD) measurements on continuous films reveal the presence of a thin γ‐Fe2O3 interlayer. The nanodots retain key crystallographic and magnetic properties of continuous films, including the Verwey transition, while exhibiting reproducible bipolar resistive switching at the nanoscale. This combined structural, magnetic, and electrical characterization establishes a robust platform for integrating ordered magnetite nanostructures into functional oxide‐based nanoelectronic devices.