Template-free generation and integration of functional 1D magnetic nanostructures

Abstract

This work reports on a novel template-free technique for producing isolated 1D magnetic nanochains and nanowires directly onto substrates and device architectures by directed self-assembly of gas-phase-generated nanoparticles.

Single-step generation of 1D FeCo nanostructures

“…Furthermore, the approach opens up for controlling and studying the self-assembly from the first particle, exemplified here by following the growth of individual NCs, particle by particle, and demonstrating how the average chain length can be controlled by adjusting the deposited particle concentration. Moreover, the technique provides a facile fabrication of free-standing 1D structures that allow for direct integration into devices, as recently demonstrated for Co NCs [14]. Finally, by combining magnetometry, x-ray microscopy, and micromagnetic simulations, we demonstrate that arranging the NPs into NCs leads to a significant shape anisotropy and that local variations in the magnetocrystalline anisotropy along the chains play a key role in the domain formation.…”

“…As the vapor cools down, condensation of sub-10nm primary particles takes place, which then form larger irregular agglomerates by collision. To avoid oxidation of particles, a carrier gas composed of 95% N 2 and 5% H 2 (1.68 lpm) is used, and the pressure of the gas is kept constant at around 1015 mbar [14,38,40]. The agglomerates are then passed to a Ni 63 bipolar diffusion charger to give an even charge distribution to the materials.…”

“…The resulting NPs are then size-selected based on their electric mobility and attracted to the substrate using an electric field. The substrate is placed on a NdFeB magnet, and as the NPs arrive at the surface, they self-assemble via magnetic dipole-dipole interactions to form 1D NCs along the direction of the applied field [14,34], as illustrated in figure 1(a). The NPs in this work are not monodispersed.…”

“…Self-assembling functional nanoscopic building blocks, such as nanoparticles (NPs), into larger structures is a promising strategy for generating tailored functional materials [1][2][3]. In particular, linear arrangement of NPs, so-called nanochains (NCs), exhibit anisotropic properties and are explored for applications in bio-medicine [4,5], as contrast agents [6], microwave absorption [7,8], catalysis [9,10], plasmonics [11,12], memory applications [13], and magnetic field and gas sensing [14][15][16].…”

“…Herein, we present a bottom-up approach for generating metallic FeCo alloy NPs and self-assembling them into parallel NCs with controlled average length directly along a substrate surface. The approach combines the simplicity of magnetic-field-directed self-assembly with the added control of using electric fields to attract charged aerosol NPs to the surface [14,34]. The method employs an aerosol technique based on spark ablation where NPs are generated by a discharge between two electrodes and transported away with a carrier gas at ambient pressure [35].…”