Dispersion‐Controlled Gold–Aluminum–Silicon Dioxide–Aluminum Nanopawn Structures for Visible to NIR Light Modulation

Abstract As an efficient patterning method for nanostructures, nanocolloidal lithography (NCL) presents a controllable and scalable means for achieving a uniform and good sidewall profile, and a high aspect ratio. While high selectivity between the etching mask and targeted materials is also essential for NCL‐based precision nanophotonic structures, its realization in multi‐material nanophotonic structures still remains a challenge due to the dielectric‐ or metallic‐material‐dependent etching selectivity. Here, dispersion‐controlled Au‐NCL is proposed, which enables high selectivity for Al and SiO₂ over a Au nanoparticle (Au‐NP) mask. Utilizing the proposed process, wafer‐scale, uniformly dispersed multi‐material nanopawn structures (Au‐NPs/Al–SiO₂ cylinders) on an Al ultrathin film are realized, obtaining excellent vertical sidewall (≈90°) and aspect ratio (>1). The high sidewall verticality and aspect ratio of the nanopawn structures support optical modes highly sensitive to the excitation direction of incident waves through the mixing of the interface‐gap‐assisted localized surface plasmons (GLSPs) formed in between the Au‐NP and Al‐disk interface, and plasmonic Fabry–Pérot (FP) modes formed in between the Al‐disk and Al substrate; complementary spectral responses between reflected and scattered light are also demonstrated. As an application example, information encryption based on the triple‐channel (i.e., reflection, scattering, and transmission) angle‐dependent complementary‐color responses is presented.