Tunable Ultra-high Aspect Ratio Nanorod Architectures grown on Porous Substrate via Electromigration.

Ali Mansourian,Gema Vizcay-Barrena,Anatoly V Zayats,Samjid H Mannan,Roland A Fleck,Seyed Amir Paknejad,Qiannan Wen

doi:10.1038/srep22272

Ali Mansourian, Gema Vizcay-Barrena + Show 5 more

Open Access

https://doi.org/10.1038/srep22272

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Abstract

The interplay between porosity and electromigration can be used to manipulate atoms resulting in mass fabrication of nanoscale structures. Electromigration usually results in the accumulation of atoms accompanied by protrusions at the anode and atomic depletion causing voids at the cathode. Here we show that in porous media the pattern of atomic deposition and depletion is altered such that atomic accumulation occurs over the whole surface and not just at the anode. The effect is explained by the interaction between atomic drift due to electric current and local temperature gradients resulting from intense Joule heating at constrictions between grains. Utilizing this effect, a porous silver substrate is used to mass produce free-standing silver nanorods with very high aspect ratios of more than 200 using current densities of the order of 108 A/m2. This simple method results in reproducible formation of shaped nanorods, with independent control over their density and length. Consequently, complex patterns of high quality single crystal nanorods can be formed in-situ with significant advantages over competing methods of nanorod formation for plasmonics, energy storage and sensing applications.

Highlights

Electromigration (EM) is defined as the transport of atoms driven by momentum transfer from electron flow inside a current carrying material
EM has been used as a constructive process leading to mass fabrication of nanorods by passing current through a stripe of porous material under controlled current density
Absence of grain refinement at the surface of the substrate, Energy Dispersive X-Ray (EDX) measurements on the nanorods, heated samples and interrupted EM experiments all indicate that an oxide layer on the exterior Ag surface restricts atomic diffusion here and allows compressive stress build up leading to nanodot and nanorod formation at weak points of the oxide layer

Summary

Introduction

Electromigration (EM) is defined as the transport of atoms driven by momentum transfer from electron flow inside a current carrying material. This can lead to structural changes such as whisker growth and stress induced voids[1,2]. The simplicity of nanorod formation by electromigration, utilizing voltages ~7 mV across the ~500 μm length of the conducting stripe to generate high current density, may have significant advantages over other methods of nanorod growth[20] and in particular may allow complex patterns of nanorods being grown by controlling the local current densities

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Discussion

Conclusion