Large‐Scale Plasmonic Hybrid Framework with Built‐In Nanohole Array as Multifunctional Optical Sensing Platforms

Abstract

Light coupling with patterned subwavelength hole arrays induces enhanced transmission supported by the strong surface plasmon mode. In this work, a nanostructured plasmonic framework with vertically built‐in nanohole arrays at deep‐subwavelength scale (6 nm) is demonstrated using a two‐step fabrication method. The nanohole arrays are formed first by the growth of a high‐quality two‐phase (i.e., Au–TiN) vertically aligned nanocomposite template, followed by selective wet‐etching of the metal (Au). Such a plasmonic nanohole film owns high epitaxial quality with large surface coverage and the structure can be tailored as either fully etched or half‐way etched nanoholes via careful control of the etching process. The chemically inert and plasmonic TiN plays a role in maintaining sharp hole boundary and preventing lattice distortion. Optical properties such as enhanced transmittance and anisotropic dielectric function in the visible regime are demonstrated. Numerical simulation suggests an extended surface plasmon mode and strong field enhancement at the hole edges. Two demonstrations, including the enhanced and modulated photoluminescence by surface coupling with 2D perovskite nanoplates and the refractive index sensing by infiltrating immersion liquids, suggest the great potential of such plasmonic nanohole array for reusable surface plasmon‐enhanced sensing applications.

Recent Advances in Vertically Aligned Nanocomposites with Tunable Optical Anisotropy: Fundamentals and Beyond

“…In parallel of investigating those potential issues, one can take advantage of such as-grown metamaterials to realize nanoscale coupling of multifunctional phases with inch-scale coverage, to avoid redundant fabrication processes and achieve mass-production of nanodevices. So far, some successful demonstrations of sensing have been achieved, including TiN-Au metasurface for chemical bonding detection [70], microfluidic sensing using TiN nanoholes [72], and TiN-Ag nanocomposite as a high-temperature angular reflector [53]. These studies present great potential and pave the way for applying similar tests to other oxide-metal VANs systems.…”

“…Using a two-step growth and chemical etching process, an epitaxial TiN nanohole film has been reported. Here, the 6-nm "air gaps" (Figure 4f) generates strong optical anisotropy as represented by the ordinary and extraordinary dielectric tensors in Figure 4e [72]. Different from conventional methods of nanohole fabrication, such as EBL or laser imprinting, using bottom-up deposition of TiN-Au VAN followed by chemical etching to remove Au nanopillars produces large-scale throughput and ultrafine holes with reasonable ordering.…”

“…All of these examples have shown great potentials in achieving various artificial metamaterial designs possessing relatively good periodicity, large-scale surface coverage, epitaxial quality, atomic-sharp interface, as well as tunable functionalities. Table 1 summarizes the recent ceramic-based wire metamaterials (or VANs) grown by physical vapor deposition technique, and their reported functionalities [51][52][53][54][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70][71][72][73][74]. The ultimate goal is to realize an alternative method in fabricating functional heterostructures or metamaterials for applications including sensing, high-temperature plasmonics, nonlinear optics, ultrafast switching, as well as fundamental explorations, including tunable plasmonics or coupled multifunctionalities, using these highly anisotropic media.…”

“…Here, we present few examples on coupling growth designs to realize capabilities such as sensing, magnetooptical coupling, as well as high-temperature plasmonics. As briefly mentioned in the earlier discussion, the design of plasmonic TiN nanoholes is realized through removal of Au phase from a highly-ordered TiN-Au VAN template (Figure 8a) [72]. The nanoscale air holes generate strong LSPs close to the edge of TiN metasurfaces, which are highly sensitive to the change of local refractive indices and can be applied for sensing.…”

Nitride‐Oxide‐Metal Heterostructure with Self‐Assembled Core–Shell Nanopillar Arrays: Effect of Ordering on Magneto‐Optical Properties

“…It is noted that the TiN‐Au template offers tuning flexibility and has been recently applied in creating high‐quality TiN nanoholes. [ 51 ]…”