Large‐Area Periodic Arrays of Atomically Flat Single‐Crystal Gold Nanotriangles Formed Directly on Substrate Surfaces

Abstract

The advancement of nanoenabled wafer‐based devices requires the establishment of core competencies related to the deterministic positioning of nanometric building blocks over large areas. Within this realm, plasmonic single‐crystal gold nanotriangles represent one of the most attractive nanoscale components but where the formation of addressable arrays at scale has heretofore proven impracticable. Herein, a benchtop process is presented for the formation of large‐area periodic arrays of gold nanotriangles. The devised growth pathway sees the formation of an array of defect‐laden seeds using lithographic and vapor‐phase assembly processes followed by their placement in a growth solution promoting planar growth and threefold symmetric side‐faceting. The nanotriangles formed in this high‐yield synthesis distinguish themselves in that they are epitaxially aligned with the underlying substrate, grown to thicknesses that are not readily obtainable in colloidal syntheses, and present atomically flat pristine surfaces exhibiting gold atoms with a close‐packed structure. As such, they express crisp and unambiguous plasmonic modes and form photoactive surfaces with highly tunable and readily modeled plasmon resonances. The devised methods, hence, advance the integration of single‐crystal gold nanotriangles into device platforms and provide an overall fabrication strategy that is adaptable to other nanomaterials.

Plate-Like Colloidal Metal Nanoparticles

“…Progress in various self-assembly techniques allows for organizing randomly distributed metal nanoplates from colloidal dispersions into monolayers on substrates, , close-packed assemblies, , colloidal dimers or clusters, − periodic arrays, − and 3D superlattices . Self-assembly can be regarded as an effective approach to tailor the collective optical properties of metal nanoplates and to incorporate them into functional substrates. , …”

Infrared Near-Field Spectroscopy of Gold Nanotriangle Fabry-Pérot Resonances

“…The Au NT synthesis was adapted from a prior study demonstrating the formation of substrate-immobilized nanotriangles in periodic arrays on (0001)-oriented Al 2 O 3 . 31 The overall process yields singlecrystal Au seeds formed in periodic arrays 46 after which they are subjected to a liquid-phase synthesis that transforms them into Au NTs. Here, adaptations were made to accommodate the use of SiN x TEM grids as the substrate material.…”

“…29 Alternatively, electron-beam lithography can synthesize gold NTs of desired edge lengths 30 but this method significantly increases the cost. To circumvent this problem, we recently devised a new approach for the colloidal synthesis of uniform thickness and controllable edge-length gold NTs directly on substrates 31 and here we employ this synthetic method to study the near-field responses of NTs throughout the visible-to-IR spectral region.…”

Generalization of Self‐Assembly Toward Differently Shaped Colloidal Nanoparticles for Plasmonic Superlattices

“…In a recent publication, Neal et al demonstrate the synthesis of regular large-area, single triangular particle arrays, formed by EBLassisted liquid-phase growth. [21] Self-assembly of colloidal NP, on the other hand, is a lowcost and fast alternative for producing plasmonic superlattices. [22] Progress in the synthesis of monodisperse colloidal NPs makes the production of useful building blocks with close-packed clusters of NPs possible.…”

“…demonstrate the synthesis of regular large‐area, single triangular particle arrays, formed by EBL‐assisted liquid‐phase growth. [ 21 ]…”