Large-Scale Fabrication of Porous Gold Nanowires via Laser Interference Lithography and Dealloying of Gold–Silver Nano-Alloys

Adrien Chauvin,Ishan Wathuthanthri,Pierre-Yves Tessier,Nicolas Stephant,Abdel-Aziz El Mel,Ke Du,Junjun Ding,Chang-Hwan Choi

doi:10.3390/mi8060168

Abstract

In this work, we report on an efficient approach to fabricating large-area and uniform planar arrays of highly ordered nanoporous gold nanowires. The approach consists in dealloying Au–Ag alloy nanowires in concentrated nitric acid. The Au–Ag alloy nanowires were obtained by thermal annealing at 800 °C for 2 h of Au/Ag stacked nanoribbons prepared by subsequent evaporation of silver and gold through a nanograted photoresist layer serving as a mask for a lift-off process. Laser interference lithography was employed for the nanopatterning of the photoresist layer to create the large-area nanostructured mask. The result shows that for a low Au-to-Ag ratio of 1, the nanowires tend to cracks during the dealloying due to the internal residual stress generated during the dealloying process, whereas the increase of the Au-to-Ag ratio to 3 can overcome the drawback and successfully leads to the obtainment of an array of highly ordered nanoporous gold nanowires. Nanoporous gold nanowires with such well-regulated organization on a wafer-scale planar substrate are of great significance in many applications including sensors and actuators.

Highlights

Tremendous efforts have been dedicated to the development of scalable and efficient fabrication approaches of nanoporous materials since they exhibit exceptional properties, allowing them to be used in a large spectrum of applications including catalysis [1,2], sensors [3,4], and actuators [5,6]
Laser interference lithography is applied to pattern the photoresist mask and create an array of periodic nanograte structures with a height of 200 nm and a pitch of 240 nm, which serve as a mask for metal deposition (Figure 1b)
Growth of AAuu––AAgg aallllooyynnaannoowwiirreessaannddddeeaalloloyyiningg. .TThheeAAuu//Ag stacked layers used to create the Au–Ag alloy nanowires were deposited through the photoresist mask by e-beam evaporation (Lesker Inc., Jeffeerrssoonn HHiillllss, PPAA,UUSSAA))..PPrriioorrttootthheeAAuu//Ag deposition, a 10 nm Cr adhesion layer was depositeedd ththrroouugghhthtehemamsakstko etonseunresuaregoaodgoadodheasidohneasniodnmaencdhamnieccahl astnaibcaillitystoabf itlhiteyAouf/tAhge sAtauc/kAedg lsataycekrsedtoltahyeesrus btsotrtahte asnudbsatvraotied daneldamavinoaidtiodneilsasmueinsadtuiorningissthueeslifdt-uorfifnpgrotcheedulirfte-o(if.fe.p, reomceodvuarleof(it.he.e, prehmotoovraelsiosft tmheaspkhiontoprierasinsht amsaoslkutiinonp)i.ranha solution)

Summary

Introduction

Tremendous efforts have been dedicated to the development of scalable and efficient fabrication approaches of nanoporous materials since they exhibit exceptional properties, allowing them to be used in a large spectrum of applications including catalysis [1,2], sensors [3,4], and actuators [5,6]. The fabrication of the nanoporous materials in one-dimensional arrays of nanowires improves the functional properties of the material in comparison to thin films due to the very high aspect ratio of such one-dimensional structures that allows enhancing their active specific surface area [23,24,25]. In comparison to nanoparticles, creating organized arrays of nanoporous nanowires over a large substrate area enables a simple integration of such functional materials in micro/nano-devices due to the simplicity in the manipulation [26]. We have reported on a new approach to creating highly ordered and ultra-long planar arrays of nanoporous gold nanowires, combining wafer-scale laser interference lithography and a dealloying of gold–copper (Au–Cu) nano-alloys [29,30]. The influence of the Au-to-Ag ratio on the final organization and porosity of the nanowire is investigated

Fabrication Scheme

Materials and Methods

Results