Epitaxial Ni/Cu Superlattice Nanowires with Atomically Sharp Interfaces for Spin Transport

The importance of microstructure increases when decreasing the size of an object to the nanoscale, along with the complexity of controlling it. For instance, it is particularly complicated to create nano-object with controlled interfaces. Therefore, progressing towards 1D epitaxial nanostructures poses a challenge, and realization of their full potential is linked to technological issues of achieving large-scale, precise atom stacking of two or more different chemical elements. Achieving such coherent, epitaxial interfaces is a key step toward enabling spintronic phenomena in 1D objects, by minimizing interface scattering and strain-driven defects. Our results demonstrate a successful realization of controlled nanoscale heteroepitaxy in one-dimensional single-crystal structures. We fabricated nanowires composed of alternating magnetic (nickel) and non-magnetic, highly conductive (copper) segments. This periodic stacking modulates electron transport under magnetic stimuli. The epitaxial precision achieved eliminates detrimental electron scattering that has historically limited the magnetotransport properties of such 1D structures and hindered their development. Such materials are crucial for further advancements in the miniaturisation of nanosensors, actuators, and next-generation 3D spintronic devices.

💡 Research Summary

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The paper reports the successful synthesis of epitaxial nickel/copper (Ni/Cu) superlattice nanowires (NWs) with atomically sharp interfaces, and demonstrates their spin‑transport properties. Using template‑pulsed electrodeposition (TPED) into anodic aluminum oxide (AAO) membranes, the authors produced arrays of single‑crystal NWs with a diameter of ~55 nm, length of ~3.5 µm, and a filling efficiency above 80 %. By carefully timing the voltage pulses, Ni and Cu were deposited alternately under near‑equilibrium conditions, allowing each new segment to nucleate on the existing crystal lattice without creating misoriented grains.

Structural characterization confirmed the epitaxial relationship between the two metals. X‑ray diffraction (XRD) displayed distinct Ni(111) and Cu(111) peaks together with ±1 satellite reflections, indicating a well‑ordered periodicity (e.g., 10 nm Ni / 5 nm Cu). Scanning and high‑angle annular dark‑field (HAADF) STEM revealed a wedge‑shaped, faceted cross‑section bounded by {111} and {100} facets, a morphology that deviates from the usual cylindrical wires and reflects the influence of crystallography on growth anisotropy. Energy‑dispersive X‑ray spectroscopy (EDXS) maps showed clear compositional segregation, while high‑resolution TEM and selected‑area electron diffraction (SAED) demonstrated that both Ni and Cu share the same crystallographic orientation, obeying the (110)