High Volume-Per-Dose and Low Resistivity of Cobalt Nanowires Grown by Ga+ Focused Ion Beam Induced Deposition.

Sanz-Martín Sanz-Martín,Teresa Teresa,Magén Magén

doi:10.3390/nano9121715

Sanz-Martín Sanz-Martín, Teresa Teresa + Show 1 more

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https://doi.org/10.3390/nano9121715

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Abstract

The growth of ferromagnetic nanostructures by means of focused-Ga+-beam-induced deposition (Ga+-FIBID) using the Co2(CO)8 precursor has been systematically investigated. The work aimed to obtain growth conditions allowing for the simultaneous occurrence of high growth speed, good lateral resolution, low electrical resistivity, and ferromagnetic behavior. As a first result, it has been found that the competition between deposition and milling that is produced by the Ga+ beam is a limiting factor. In our working conditions, with the maximum available precursor flux, the maximum deposit thickness has been found to be 65 nm. The obtained volumetric growth rate is at least 50 times higher than in the case of deposition by focused-electron-beam-induced deposition. The lateral resolution of the deposits can be as good as 50 nm while using Ga+-beam currents lower than 10 pA. The high metallic content of the as-grown deposits gives rise to a low electrical resistivity, within the range 20–40 µΩ·cm. Magnetic measurements confirm the ferromagnetic nature of the deposits at room temperature. In conclusion, the set of obtained results indicates that the growth of functional ferromagnetic nanostructures by Ga+-FIBID while using the Co2(CO)8 precursor is a viable and competitive technique when compared to related nanofabrication techniques.

Highlights

Magnetic nanostructures are under development for various applications, such as hard-disk memories [1], magnetic random access memories [2], drug delivery [3], magnetic hyperthermia [4], magnetic resonance imaging [3], neuromorphic computing [5], etc
We have systematically explored the possibility of using a Ga+ focused ion beam to grow Co magnetic nanostructures with good lateral resolution, low electrical resistance, and high growth speed by means of the Focused Ion Beam Induced Deposition (FIBID) technique
The Co nanowires (NWs) were grown by FIBID in a commercial Helios Nanolab 600 Dual Beam equipment (FEI company, Hillsboro, OR, USA), with the Ga+ ion source being operated at 30 kV and a Gas Injection System (GIS) delivering Co2(CO)8 as gas precursor into the chamber with typical base pressure of ~3.5 × 10−6 mbar and GIS temperature of 29 ◦C

Summary

Introduction

Magnetic nanostructures are under development for various applications, such as hard-disk memories [1], magnetic random access memories [2], drug delivery [3], magnetic hyperthermia [4], magnetic resonance imaging [3], neuromorphic computing [5], etc Their controlled fabrication is key in achieving the required functionality, given that the magnetic properties are greatly affected by features, such as dimensions, topology, surface roughness, interfacing, defects, crystal structure, etc. Focused Electron Beam Induced Deposition (FEBID) is one of the existing techniques for the growth of magnetic nanostructures, as recently reviewed [8,9]. The capability of FEBID for the growth of complex three-dimensional (3D) magnetic structures is being explored in the rising field of 3D nanomagnetism [26]

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