arXiv subjects

Aurys Silinga

Publications and source records attributed to Aurys Silinga.

4 recordsLinked to original sources

arXiv2026

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

Focused electron beam induced deposition (FEBID) is an additive manufacturing technique uniquely suited for fabricating nanoscale 3D prototypes for a range of applications, including spintronic devices. However, 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. 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 translation, we fabricated 41 Co and Fe nanowire (NW) structures with growth angle relative to the optic axis varying from 0{\deg} to 90{\deg}. 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 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{\deg} to 60{\deg} 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.

cond-mat.mes-hall↗

arXiv2024

Atomic resolution imaging of the strength and 3D direction of atomic displacements in functional oxide thin films

Atomic resolution imaging is key to understanding thin film growth and how a particular set of conditions influences properties. Whilst such imaging in the scanning transmission electron microscope (STEM) has had transformative impact in nanoscience, it forms projection images and provides no direct information about displacements perpendicular to the image plane. In this article we show that it is possible to make atomic resolution maps of the direction and magnitude of La displacements at ~30{\deg} to the imaging plane in a La2CoMnO6 thin film on (111) LSAT (LaAlO3-La(Sr,Ta)O3) using a 4-dimensional STEM (4DSTEM) methodology. This reveals that the La modulation lies preferentially in the interface plane, and is strongly suppressed close to the epitaxial interface, and further reveals how the modulation varies with distance from the interface with unit cell resolution. These details would be completely invisible to all prior techniques in electron microscopy and this sheds light on why this particular substrate in this orientation best promotes double perovskite cation ordering, and the consequent optimal magnetic ordering for this thin film system. The approach used herein of fitting atomic resolution 4DSTEM data to determine crystal parameters opens the door for a new era of atomic-resolution crystallography.

cond-mat.mtrl-sci↗

arXiv2024

Model-Based Iterative Reconstruction of Three-Dimensional Magnetisation in a Nanowire Structure Using Electron Holographic Vector Field Tomography

Methods for characterisation of 3D magnetic spin structures are necessary to advance the performance of 3D magnetic nanoscale technologies. However, as the component dimensions approach the nanometre range, it becomes more challenging to analyse 3D magnetic configurations with the appropriate spatial resolution. In this paper, we present a method based on Lorentz transmission electron microscopy in which model-based iterative reconstruction (MBIR) is used to reconstruct the most probable magnetisation in an exemplar nanostructure. This method is based on relating electron phase measurements to the magnetic configuration of the nanostructure, and therefore, the method is subject to certain limitations. In this proof-of-concept experiment, MBIR was tested on an L-shaped ferromagnetic cobalt nanowire, fabricated using focused electron beam induced deposition. Off-axis electron holography was used to acquire a tomographic tilt series of electron holograms, which were analysed to measure magnetic electron phase shift over two tilt arcs with up to $ \pm 60$ degree tilt range. Then, a 3D magnetisation vector field consistent with the tomographic phase measurements was reconstructed, revealing multiple magnetic domains within the nanowire. The reconstructed magnetisation is accurate for magnetic domains larger than 50 nm, and higher resolution can be achieved by the continued development of tomographic reconstruction algorithms.

cond-mat.mes-hall↗

arXiv2022

Measurement of atomic modulation direction using the azimuthal variation of first order Laue zone electron diffraction

We show that diffraction intensity into the First Order Laue Zone (FOLZ) of a crystal can have a strong azimuthal dependence, where this FOLZ ring appears solely because of unidirectional atom position modulation. Such a modulation was already known to cause the appearance of elliptical columns in atom resolution images, but we show that measurement of the angle via 4-dimensional Scanning Transmission Electron Microscopy (4DSTEM) is far more reliable and allows the measurement of the modulation direction with a precision of about 1{\deg} and an accuracy of about 3{\deg}. This method could be very powerful in characterising atomic structures in 3 dimensions by 4DSTEM, especially in cases where the structure deviates from that found in bulk crystals.

cond-mat.mtrl-sci↗