Self‐Assembled Metal–Dielectric Hybrid Metamaterials in Vertically Aligned Nanocomposite Form with Tailorable Optical Properties and Coupled Multifunctionalities

Abstract

Metal–dielectric hybrid metamaterials have attracted increasing research interest in recent years because of their novel optical properties and promising applications in the fields of electronic and photonic devices. Dielectric permittivity is a key parameter that strongly influences the optical properties of materials. By self‐assembling the metallic and dielectric components in a pillar‐in‐matrix structure, a strong anisotropic structure forms and results in opposite signs of permittivity components (i.e., ε|| > 0 and ε⊥ < 0, or vice versa) and exotic optical responses including hyperbolic dispersion in the visible to near‐infrared region. Herein, the main approaches of tuning the permittivity in self‐assembled metal–dielectric vertically aligned nanocomposite (VAN) thin films are reviewed, including tuning the metal pillar density and geometry, film strain state and background pressure during growth, and seeking other metal‐free and complex structure designs. Future research directions are also proposed, including unique approaches to improve their thermal stability, integrate on flexible substrates toward wearable device fabrication, and explore real‐time tunable metamaterials.

Visible-Range Multiple-Channel Metal-Shell Rod-Shaped Narrowband Plasmonic Metamaterial Absorber for Refractive Index and Temperature Sensing

“…Metamaterials are artificial materials composed of nanometer-sized hybrid metal-dielectric nanostructures which can attain unique electromagnetic (EM) characteristics that cannot be found naturally [ 1 , 2 , 3 ]. Plasmonic metamaterials can be used to trap the EM wave in the nanometer regime and beyond the diffraction limit of traditional optics [ 4 , 5 , 6 ].…”

Self-assembled HfO2-Au nanocomposites with ultra-fine vertically aligned Au nanopillars

“…Metamaterials are artificial materials that exhibit extraordinary optical, electrical, and mechanical properties that are difficult to achieve in natural materials. [1][2][3][4] The metamaterials' unique properties make them valuable for applications in various fields, including chemical catalysis, 5,6 optics, 7 and sensors. 8 Recently significant work has been focused on enabling the multifunctionality and tunability of these metamaterials.…”

Strong Interfacial Coupling of Tunable Ni–NiO Nanocomposite Thin Films Formed by Self-Decomposition

“…27−29 The vertically aligned cylindrical nanopillars can be well coupled with the matrix phase, the aspect ratio and density can be tailored by varying the growth parameters or the target ratio, and so do their magnetic properties and exchange bias coupling properties. 30 Most of these two-phase nanocomposite systems involve either cogrowth of two different oxides 31,32 codeposition of a metal with an oxide, 28,33 which are often limited by materials compatibility and chemical stability.…”

“…For example, FM lanthanum strontium manganite (La 1 –x Sr x MnO 3 or LSMO) perovskite oxide has been coupled with AFM oxides such as NiO, BiFeO 3 , and LaFeO 3 . − Such self-assembly process is realized by the variations of nucleation property between the two constituent phases, i.e., the matrix phase favors the layered growth mode while the pillar phase favors the islanded growth mode. − The vertically aligned cylindrical nanopillars can be well coupled with the matrix phase, the aspect ratio and density can be tailored by varying the growth parameters or the target ratio, and so do their magnetic properties and exchange bias coupling properties . Most of these two-phase nanocomposite systems involve either cogrowth of two different oxides , or codeposition of a metal with an oxide, , which are often limited by materials compatibility and chemical stability.…”