Fabrication of Au nanorod and nanogap split-ring structures by reactive-monolayer-assisted thermal nanoimprint lithography involving electrodeposition

Abstract

Au nanorods and Au nanogap split-ring (SR) structures were fabricated to investigate the ability of wet etching and Ar ion milling processes to remove an underlying Au electrode layer on shapes of electrodeposited Au structures. A reactive-monolayer-assisted thermal nanoimprint lithography process involving Au electrodeposition was used to make 100 nm × 500 nm Au nanorods and Au nanogap SR structures with widths of 125 nm and two 20 nm gaps. Individual Au bump structures were successfully demonstrated on transparent silica substrates by Ar ion milling and subsequent Cr wet etching. Au nanorod and nanogap SR structures were obtained almost uniformly over a 100-μm square area, which was sufficient to investigate their optical properties. The array comprising electrodeposited Au nanorods showed an anisotropic absorption band, attributable to a transverse plasmon band at wavelengths ranging from 500 to 700 nm when an incident light was linearly polarized perpendicular to the long axis of Au nanorods.