Compositional and Magnetic Characterisation of Oblique Co and Fe Nanowire Structures Fabricated Using Focused Electron Beam Induced Deposition

arXiv:2605.14673 · cond-mat.mes-hall, cond-mat.mtrl-sci · Submitted 2026-05-14 · Read on arXiv

Listen

Transcript

Introduction to the show: ident: Quantum Radio. Generated commentary on the latest quantum physics and condensed matter papers.

Kai: Today's paper: "Compositional and Magnetic Characterisation of Oblique Co and Fe Nanowire Structures Fabricated Using Focused Electron Beam Induced Deposition".

Mira: The gist: The study measures changes in atomic composition and corresponding changes in magnetic induction in 3D ferromagnetic nanostructures fabricated using Focused Electron Beam Induced Deposition,

Kai: First, who's behind it and why it matters.

Paper summary: Kai: So we’re looking at this paper now called "Compositional and Magnetic Characterisation of Oblique Co and Fe Nanowire Structures Fabricated Using Focused Electron Beam Induced Deposition". The main idea here is that when you make these three-dimensional nanostructures using FEBID, the way you move the electron beam changes how much metal is actually in the nanowires.

Mira: Right, so it’s about this variation in growth dynamics causing non-uniform composition when building complex three dee geometries like bridges or arches one <ref:2605.14673#pg1>. This study measures those changes in atomic composition and magnetic induction for these structures with overhanging elements. It matters because if we want to build spintronic devices, we need that material purity to be consistent across the whole structure.

Lev: From an error correction standpoint, inconsistent composition is a real problem because it introduces random magnetic effects that you can't predict when trying to run them on real hardware three <ref:2605.14673#pg1>. We need predictable materials for reliable quantum circuits.

Kai: Exactly, and this paper investigates how much the metal content changes as you adjust the growth angle of these nanowires, testing angles from zero degrees up to ninety degrees. They use SEM techniques like electron energy loss spectroscopy and off-axis electron holography to map out what's going on at the atomic level and how magnetic they are.

Mira: The core claim they make is that there’s a reduction in metal content as you increase the oblique growth angle in these FEBID nanowires one <ref:2605.14673#pg1>. They found that this reduction in metal content can actually be tuned by adjusting the electron beam parameters, like voltage and current.

Lev: It sounds like they have specific settings where they managed to keep the metal content pretty similar across different angles, for example, between zero degrees and sixty degrees. How did they achieve that balance?

Kai: They suggest using the lowest viable electron beam voltage and the highest viable beam current to reduce the interaction volume, which apparently increases the metal content three <ref:2605.14673#pg1>. But they also found that higher beam currents can lead to surface nodules because of autocatalytic deposition three <ref:2605.14673#pg1>.

Mira: And for oblique structures specifically, they found a combination of parameters—specifically a five kilovolt accelerating voltage, two point eight nanoamperes beam current, and the Fe2(CO)nine precursor gas—that gave them the most symmetrical and highest purity oblique nanowires without needing any annealing one <ref:2605.14673#pg2>.

Lev: That's a specific recipe for getting good material quality when you’re going oblique. But what are we actually measuring with this magnetic induction stuff? What does that tell us about the structure?

Kai: They use off-axis electron holography to reconstruct the magnetic phase shift, which lets them calculate the magnetic induction, or B field one <ref:2605.14673#pg1>. They found that in both Cobalt and Iron samples, nanowires grown at larger angles have a lower percentage of metal atoms overall.

Mira: And they quantified that drop in the B field—it’s two milliTesla per degree theta for Co and seven milliTesla per degree theta for Fe one <ref:2605.14673#pg1>. That’s a measurable change linked directly to the composition shift.

Lev: So, if I'm driving, this means when I build these structures, choosing a different angle isn't just changing the shape; it's actively changing the magnetic properties of the wire itself. What does that mean for someone who is only listening to this show?

Kai: It means that for spintronic devices, where you rely on precise magnetic behavior, you have to be very careful about how you deposit these nanoscale wires because the angle you choose directly impacts how much metal is there and consequently how strong the magnetic field will be one <ref:2605.14673#pg1>.

Mira: It’s about showing that we can control these properties by tuning deposition parameters rather than just accepting whatever happens when we use a translating beam one <ref:2605.14673#pg1>.

Lev: And from a hardware perspective, understanding this dependence on angle means you can design fabrication processes that account for the composition change before you even start the etching phase three <ref:2605.14673#pg1>.

Kai: So, to wrap up this segment, they've shown how changing the growth angle affects both the elemental composition and the resulting magnetic induction in these FEBID nanowires. This sets up a clear path for us to control these properties better. Next up, we’re going to talk about what it means for circuit design and optimization.

Conclusion: Kai: We’ve looked at this paper, "Compositional and Magnetic Characterisation of Oblique Co and Fe Nanowire Structures Fabricated Using Focused Electron Beam Induced Deposition," by Aurys Šilinga, Keir Edgar, András Kovács, Stephen McVitie, Rafal E. Dunin-Borkowski, Kayla Fallon, and Trevor P. Almeida one <ref:2605.14673#pg1>.

Mira: The main implication is that for those designing spintronic circuits using these nanoscale wires for data storage or neural networks two, they can now have a way to minimize the material inconsistency caused by the growth process one <ref:2605.14673#pg1>.

Lev: Essentially, it suggests that if you want consistent magnetic behavior from your fabricated components, you need to control the deposition parameters tightly to keep that metal content stable across different angles three <ref:2605.14673#pg1>.

Kai: So, in simple terms for someone who just listens to this show, this research proves that the angle of growth isn't just a geometric choice anymore; it’s a material property choice one <ref:2605.14673#pg1>.

Mira: It means we can design deposition processes that confine the reaction reactions to a tiny volume inside the wire diameter using specific voltage and gas choices one <ref:2605.14673#pg1>.

Lev: And for error correction, this gives you a better baseline for predicting how fabrication variations might affect the final magnetic state of your nanowire structures three <ref:2605.14673#pg1>.

Kai: That’s it. So we’ve seen how the angle of growth dictates the composition and magnetic induction, and that we have tools to tune those results by adjusting the deposition settings.

SUPA, School of Physics and Astronomy, University of Glasgow · Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich

cond-mat.mes-hall, cond-mat.mtrl-sci

Submitted: 2026-05-14

Updated: 2026-10-08

Journal ref: ACS Appl. Nano Mater. 2026

DOI: 10.1021/acsanm.6c02497

License: http://creativecommons.org/licenses/by/4.0/

Importance score: 75/100

The gist: The gist: The study measures changes in atomic composition and corresponding changes in magnetic induction in 3D ferromagnetic nanostructures fabricated using Focused Electron Beam Induced

Key concepts

Focused Electron Beam Induced Deposition (FEBID): FEBID is a technique used to build 3D nanoscale structures by using a focused electron beam to deposit material onto a substrate. It's an additive manufacturing method that allows for the creation of intricate 3D prototypes at the nanoscale, though it can lead to non-uniform composition depending on how the beam interacts with the sample.
Growth Angle ($ heta$): This refers to the angle at which a nanowire grows relative to its optic axis during FEBID fabrication. The study investigated how changing this angle from 0° (vertical) to 90° (oblique) affects both the elemental composition and the resulting magnetic properties of the nanowires.
Magnetic Induction ($B$ field): This measures the strength of a magnetic field within a material. In this study, researchers used off-axis electron holography to calculate this value. They found that as the growth angle increased, the magnetic induction parallel to one axis decreased significantly, directly linked to changes in the metal content.

Terminology

Calibration — 8× in this paper · explained in 7 episodes
Consistency — 7× in this paper · explained in 3 episodes
Trace — 5× in this paper · explained in 2 episodes
Core — 4× in this paper · explained in 2 episodes
Aperture — 3× in this paper · explained in 1 episode
Accuracy — 2× in this paper · explained in 1 episode
Alignment — 2× in this paper · explained in 1 episode
Anisotropy — 2× in this paper · explained in 3 episodes
Principal Component Analysis (PCA) — 2× in this paper · explained in 4 episodes
Signal-to-noise ratio (SNR) — 2× in this paper · explained in 2 episodes
Aharonov-Bohm Effect — 1× in this paper · explained in 2 episodes
Corrected Electron Optical System GmbH — 1× in this paper
Domain Walls — 1× in this paper · explained in 2 episodes
Quantum Circuits — 1× in this paper · explained in 2 episodes
Symmetry Breaking — 1× in this paper · explained in 3 episodes

Summary

The gist: The study measures changes in atomic composition and corresponding changes in magnetic induction in 3D ferromagnetic nanostructures fabricated using Focused Electron Beam Induced Deposition, revealing that a reduction in metal content occurs with increased oblique growth angle.

Fabrication and Growth Dynamics

Focused electron beam induced deposition (FEBID) is an additive manufacturing technique used for fabricating nanoscale 3D prototypes, but the variation of growth dynamics associated with electron beam translation and sample interaction volumes results in structures with non-uniform composition when fabricating intricate 3D geometries. To investigate the effects of electron beam translation, the researchers fabricated 41 Co and Fe nanowire (NW) structures with growth angle relative to the optic axis varying from 0° to 90°. The scanning transmission electron microscopy techniques of electron energy loss spectroscopy and off-axis electron holography were performed to map the NW elemental composition and magnetic induction as a function of NW growth angle.

Effect of Growth Angle on Composition

Comparison of the results reveals a reduction in metal content with increased oblique growth angle in FEBID NWs. The magnitude of metal content reduction can be tuned by controlling electron beam parameters, and ferromagnetic NWs with approximately equal metal content at growth angles from 0° to 60° were fabricated by using the lowest viable electron beam voltage and the highest viable beam current to reduce the interaction volume and increase the metal content, respectively. For Co NWs deposited with a 30 kV beam, TEM characterisation confirms that the highest purity NWs are deposited using higher beam currents and exhibit surface nodules attributed to autocatalytic deposition. Furthermore, for oblique Co NWs using a 30 kV beam, "the most symmetrical and highest purity oblique NWs (without annealing) were deposited using the combination of the lowest tested accelerating voltage (5 kV), the highest beam current (2.8 nA), and the Fe2(CO)9 precursor gas".

Characterization Techniques

Elemental mapping was performed using a JEOL ARM200cf operated at 200 kV equipped with a cold field emission gun, a CEOS probe corrector and Gatan 965 Quantum ER spectrometer to perform STEM electron energy loss spectroscopy (EELS) elemental mapping. Principal component analysis (PCA) was utilized to remove X-ray signatures and reduce noise in high-loss spectra by reconstructing from the first 150 components, such that PCA would alter quantification results by less than 0.1% in sample areas with high signal-to-noise ratio (SNR), but provide smoothing in areas of low SNR. Magnetic characterisation was performed using off-axis electron holography to reconstruct the magnetic phase shift (φm) of an electron wave passing through the sample and calculate magnetic induction (B). The thickness-averaged magnetic induction component parallel to the y-axis is given by By(x) = −¯h/e tz dφm/dx.

Magnetic Induction Trends

In both Co↗ 5 kV and Fe↗ 30 kV samples, the NWs grown at larger angles are observed to contain a lower percentage of metal atoms, and the By value reduction is 2 mT and 7 mT per degree of θ, respectively. The lowest-purity NW deposited at θ > 70◦ was observed to warp during STEM EELS mapping, creating a site where a magnetic domain wall regularly forms after saturating the sample. Overall, the B field created in ferromagnetic NWs is affected by growth angle due to changes in elemental composition.

Optimization Strategies

Strategies are discussed for optimising deposition parameters to improve material uniformity in 3D ferromagnetic FEBID nanostructures. The optimal conditions found were 5 kV accelerating voltage; 2.8 nA beam current; and the Fe2CO9 precursor gas which limited the decrease in NW metal content to 0.1%/° and preserved the cross-sectional shape for growth angles up to 60°. The paper concludes that "metal content in oblique NWs is dependent on the growth angle, but variation in material properties can be minimised by using a precursor gas and accelerating voltage that confine the deposition reactions to an interaction volume within the NW diameter".

Micromagnetic Simulations

Micromagnetic simulations were performed using Mumax3 to determine M configurations that are energetically stable in cylindrical FEBID NWs comprising nanocrystalline impure Co. The simulations show that the oblique NWs in Figure 6 are expected to be uniformly magnetised. Based on modelling of the demagnetising fields, the average B0 is expected to be from 10% to 20% greater than By for such NW geometries.

Conclusion

The work demonstrates inherent variation in the material properties of oblique FEBID NWs deposited with a translating electron beam, as compared to a stationary beam, and shows that these properties can be tuned by adjusting the deposition parameters. Ensuring uniform NW composition enhances the consistency of spintronic circuit prototypes fabricated with FEBID. The paper shows that metal content in oblique NWs is dependent on the growth angle, but variation in material properties can be minimised by using a precursor gas and accelerating voltage that confine the deposition reactions to an interaction volume within the NW diameter.

Acknowledgements

The authors thank for funding from the Engineering and Physical Science Research Council (Grant No. EP/W524359/1, EP/X025632/1), the European Research Council under the European Union’s Horizon 2020 Research and Innovation Programme (Grant No. 856538, project ’3D MAGiC’), the Deutsche Forschungsgemeinschaft (Project-ID 405553726 TRR270), and the Helmholtz fellowship.

Supporting Information

The following files are available free of charge: Supporting information.pdf: EELS scans underlying the datapoints in Figure 6, a discussion about generating the model in Figure 3, and magnetic induction maps of vertical annealed NWs underlying calibration datapoints in Figure 10a.

References

(1) Nikonov, D. E.; Bourianoff, G. I.; Gargini, P. A. Journal of Superconductivity and Novel Magnetism 2006, 19, 497–513

(2) Parkin, S. S. P.; Hayashi, M.; Thomas, L. Science 2008, 320, 190–194

(3) Ellis, M. O. A.; Welbourne, A.; Kyle, S. J.; Fry, P. W.; Allwood, D. A.; Hayward, T. J.; Vasilaki, E. Neuromorphic Computing and Engineering 2023, 3, 021001

(4) Gu, K.; Guan, Y.; Hazra, B. K.; Deniz, H.; Migliorini, A.; Zhang, W.; Parkin, S. S. P. Nature Nanotechnology 2022, 17, 1065–1071

(5) Streubel, R.; Fischer, P.; Kronast, F.; Kravchuk, V. P.; Sheka, D. D.; Gaididei, Y.; Schmidt, O. G.; Makarov, D. Journal of Physics D: Applied Physics 2016, 49, 363001

(6) Hertel, R. SPIN 2013, 03, 1340009

(7) Fernández-Pacheco, A.; Skoric, L.; De Teresa, J. M.; Pablo-Navarro, J.; Huth, M.; Dobrovolskiy, O. V. Materials 2020, 13, 3774

(8) De Teresa, J. M.; Fernández-Pacheco, A.; Córdoba, R.; Serrano-Ramón, L.; Sangiao, S.; Ibarra, M. R. Journal of Physics D: Applied Physics 2016, 49, 243003

(9) Skoric, L.; Sanz-Hernández, D.; Meng, F.; Donnelly, C.; Merino-Aceituno, S.; Fernández-Pacheco, A. Nano Letters 2020, 20, 184–191

(10) Keller, L.; Al Mamoori, M. K. I.; Pieper, J.

Improvements for AI systems

Improved Material Characterization for FEBID: The AI system can accurately predict reduction in metal content with increased oblique growth angle in FEBID NWs by correlating measured metal content with the growth angle, utilizing the correlation established in Figure 6 and Equation 1. This allows the system to determine optimal deposition parameters to maintain a desired metal content.
Predictive Optimization of Deposition Parameters: The AI can optimize beam parameters (accelerating voltage, beam current) by predicting outcomes based on observed effects like E0, E1, and E5. For instance, it can suggest the conditions that result in a structure with approximately equal metal content at growth angles from 0° to 60°, as described in the text.
Automated Geometry and Composition Mapping: The system can perform automated analysis of STEM EELS maps to model radially layered structure, consistent with a Co (or Fe) rich core and an outer shell rich in C and O, ensuring that compositional models are applied correctly to experimental data.
Magnetic Induction Prediction: The AI can calculate the thickness-averaged magnetic induction component parallel to the y-axis using Equation 4, by inputting the spatially resolved thickness measurements derived from W(γ) calculations and reconstructed magnetic phase shifts (φm). This allows for predicting the strength of magnetic induction fields created inside the NWs.
Spintronic Device Prototype Design: The AI can inform the design of spintronic devices by predicting how changes in growth angle affect the magnetic domain wall (DW) movement, which is crucial for designing magnetic racetrack memory or artificial neural networks.

Abstract

Focused electron beam induced deposition (FEBID) is an additive manufacturing technique uniquely suited for fabricating functional 3D nanostructures for a range of applications, including spintronic devices. However, the variation of growth dynamics associated with lateral movement of the electron beam results in structures with non-uniform composition when fabricating intricate 3D geometries. Herein, we measure changes in atomic composition and corresponding changes in magnetic induction in 3D ferromagnetic nanostructures with overhanging elements, e.g. bridges or arches. To investigate the effects of electron beam lateral movement, we fabricated Co and Fe nanowire (NW) structures with growth angle relative to the optic axis varying from 0° to 90°. The (scanning) transmission electron microscopy techniques of electron energy loss spectroscopy and off-axis electron holography were performed to map the NW elemental composition and magnetic induction as a function of NW growth angle. Comparison of the results reveals a reduction in metal content with increased growth angle in FEBID NWs. The magnitude of metal content reduction can be tuned by controlling electron beam parameters, and ferromagnetic NWs with approximately equal metal content at growth angles from 0° to 60° were fabricated by using the lowest viable electron beam voltage and the highest viable beam current to reduce the interaction volume and increase the metal content, respectively.