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.

Monolithic MOF-Based Metal–Insulator–Metal Resonator for Filtering and Sensing

“…Also, optical images showed a tunable variable coloration from blue to red for the MOF-based MIM resonators (Figure d). Reported MIM resonators showed angle-dependent reflection due to the constructive interference. , A higher-index dielectric spacer could mitigate the angle-dependence of the colors because the refraction angle in a high-index film remained small over a wide range of incidence angles . Notably, our MOF-based MIM resonator showed negligible angle dependence for the reflection in all three samples with different colors (Figure S3), because the HKUST-1 SURMOFs have a higher refractive index .…”

“…At the interface of a plasmonic metal and dielectric, electromagnetic surface waves can be confined in subwavelength dimensions to overcome the diffraction limit . A typical metal–insulator–metal (MIM) configuration is constructed by sandwiching a lossless dielectric layer between two highly reflective metallic films, which demonstrates efficient band-pass filtering with scalability and cost-effectiveness. − Reflected color of the MIM resonator can be controlled by varying the refractive index and thickness of the insulator. − …”

Programmable directional color dynamics using plasmonics

“…We apply the principle of localized surface plasmon resonance (LSPR), utilizing the scattering and absorption properties of subwavelength metal nanoparticles, generally with dimensions below 100 nm [24][25][26][27][28] . A key factor of this LSPR phenomenon is its susceptibility to color alteration in response to the refractive index of the nanoparticle's surrounding medium Δn 29 , reminiscent of the underlying modulation mechanism observed in the photonic structure of the deer eyes in Fig.…”