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

TL;DR

This study investigates how the composition and magnetic properties of Co and Fe nanowires fabricated via FEBID vary with growth angle, revealing controllable metal content reduction and magnetic induction changes.

Contribution

It provides a detailed analysis of compositional and magnetic variations in 3D ferromagnetic nanostructures as a function of growth angle and electron beam parameters.

Findings

Metal content decreases with increased oblique growth angle.

Metal content can be tuned by adjusting electron beam voltage and current.

Ferromagnetic nanowires with nearly equal metal content at various angles were fabricated.

Abstract

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.