Capillary-force-induced collapse lithography for controlled plasmonic nanogap structures

Inki Kim,Younghwan Yang,Wooseup Hwang,Jungho Mun,Junsuk Rho

doi:10.1038/s41378-020-0177-8

Inki Kim, Younghwan Yang + Show 3 more

Open Access

https://doi.org/10.1038/s41378-020-0177-8

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Abstract

The capillary force effect is one of the most important fabrication parameters that must be considered at the micro/nanoscale because it is strong enough to deform micro/nanostructures. However, the deformation of micro/nanostructures due to such capillary forces (e.g., stiction and collapse) has been regarded as an undesirable and uncontrollable obstacle to be avoided during fabrication. Here, we present a capillary-force-induced collapse lithography (CCL) technique, which exploits the capillary force to precisely control the collapse of micro/nanostructures. CCL uses electron-beam lithography, so nanopillars with various shapes can be fabricated by precisely controlling the capillary-force-dominant cohesion process and the nanopillar-geometry-dominant collapse process by adjusting the fabrication parameters such as the development time, electron dose, and shape of the nanopillars. CCL aims to achieve sub-10-nm plasmonic nanogap structures that promote extremely strong focusing of light. CCL is a simple and straightforward method to realize such nanogap structures that are needed for further research such as on plasmonic nanosensors.

Highlights

The capillary phenomenon occurs when a fluid flows through a narrow space and is often observed in nature[1,2,3,4,5]
We introduce the experimental procedure for realizing sub-10-nm plasmonic nanogap structures and conduct full-wave electromagnetic simulations to demonstrate the confined electric field in the nanogap region
capillary-force-induced collapse lithography (CCL) exploits a collapse phenomenon to fabricate sub-10nm plasmonic nanogap structures, which are difficult to be realized by conventional lithography

Summary

Introduction

The capillary phenomenon occurs when a fluid flows through a narrow space and is often observed in nature[1,2,3,4,5]. The deformation of micro/nanostructures due to capillary forces, such as stiction and collapse, has not been controllable and has been undesirable. To overcome these shortcomings, many researchers have suggested ways to use capillary forces to control the collapse or selfassembly of nanostructures[10,11,12,13,14,15]. The collapse of nanopillars has been reported[13], and recent

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