Sub-15-nm patterning of asymmetric metal electrodes and devices by adhesion lithography.

David J Beesley,James Semple,Aram Amassian,Lethy Krishnan Jagadamma,Martyn A Mclachlan,John C Demello,Thomas D Anthopoulos

doi:10.1038/ncomms4933

Abstract

Coplanar electrodes formed from asymmetric metals separated on the nanometre length scale are essential elements of nanoscale photonic and electronic devices. Existing fabrication methods typically involve electron-beam lithography—a technique that enables high fidelity patterning but suffers from significant limitations in terms of low throughput, poor scalability to large areas and restrictive choice of substrate and electrode materials. Here, we describe a versatile method for the rapid fabrication of asymmetric nanogap electrodes that exploits the ability of selected self-assembled monolayers to attach conformally to a prepatterned metal layer and thereby weaken adhesion to a subsequently deposited metal film. The method may be carried out under ambient conditions using simple equipment and a minimum of processing steps, enabling the rapid fabrication of nanogap electrodes and optoelectronic devices with aspect ratios in excess of 100,000.

Highlights

Coplanar electrodes formed from asymmetric metals separated on the nanometre length scale are essential elements of nanoscale photonic and electronic devices
The patterning resolution that can be achieved using a-lith compares favourably with the very few reports of aligned asymmetric nanogaps in the literature[4,5], which have utilized e-beam lithography to achieve the requisite registration of the two metals
A further technique for fabricating asymmetric nanogap electrodes was reported by Deshmukh et al.[11], who used conventional e-beam lithography to first define point-like gold electrodes with a separation of B250 nm, and electrodeposited a second metal (Co or Cu) onto one of the electrodes to narrow the gap, thereby attaining a nanometre-sized electrode separation

Summary

Introduction

Coplanar electrodes formed from asymmetric metals separated on the nanometre length scale are essential elements of nanoscale photonic and electronic devices. Existing fabrication routes entail the use of electron-beam lithography[3,4,5,6], mechanical break junctions[7,8], electrochemical deposition[9,10,11], oblique-angle shadow-evaporation[12], scanning probe lithography[13] or on-wire lithography[14] to achieve intimate registration of the two electrodes. Such methods, variously suffer from low throughput, poor scalability to larger substrate sizes, complex multi-step processing protocols, and/or high equipment costs[1,15]. The method—which can be carried out at room temperature under ambient conditions, using simple equipment and a minimum of processing steps—provides a rapid route to highly aligned, electrically isolated, asymmetric electrodes separated on the nanometre length scale

Methods

Results

Conclusion