Colloidal Self‐Assembly Meets Nanofabrication: From Two‐Dimensional Colloidal Crystals to Nanostructure Arrays

Abstract

Self-assembly of colloidal microspheres or nanospheres is an effective strategy for fabrication of ordered nanostructures. By combination of colloidal self-assembly with nanofabrication techniques, two-dimensional (2D) colloidal crystals have been employed as masks or templates for evaporation, deposition, etching, and imprinting, etc. These methods are defined as "colloidal lithography", which is now recognized as a facile, inexpensive, and repeatable nanofabrication technique. This paper presents an overview of 2D colloidal crystals and nanostructure arrays fabricated by colloidal lithography. First, different methods for fabricating self-assembled 2D colloidal crystals and complex 2D colloidal crystal structures are summarized. After that, according to the nanofabrication strategy employed in colloidal lithography, related works are reviewed as colloidal-crystal-assisted evaporation, deposition, etching, imprinting, and dewetting, respectively.

A colloidoscope of colloid-based porous materials and their uses

“…52,117 Colloidal monolayers can be especially valuable as templates or masks for etching or evaporation processes to create functional surface nanostructures or coatings. There have been intense research activities in the last decade on the generation of arrays of nanostructures using colloidal monolayers, as discussed in several recent review articles; [117][118][119][120] here, we only introduce general strategies and highlight a few examples in Figure 4A.…”

“…124 Adding directed dry etching steps to selectively remove material from defined parts of the surface further increases the accessible structures and geometries. 117,120 Figure 4A,iii shows the fabrication of arrays of crescent shaped nanoparticles by a combination of evaporation of gold under a tilted angle followed by an etching step normal to the surface. 97,125 Similarly, the colloids themselves can be used to deposit the metal using colloids that contain metal nanoparticles or molecular metal complexes as precursor materials.…”

“…In addition to 3D photonic crystals, 2D colloidal monolayers can also be tuned to create many different optical materials and properties. For example, the monolayer can be used for shadow deposition to generate different shapes of deposited materials, 97,120,124,186 used as an etch mask to generate high aspect ratio structures with high order, 166,187,188 inverted/textured to create antireflective coatings for reducing the amount of reflected light from a substrate surface, 95 or deformed to generate structurally colored patterns on a substrate. 112 Interesting coupling effects can be observed between the photonic modes of an opal and the plasmonic modes of thin metals deposited on top of the crystal.…”

Surface Patterning with Colloidal Monolayers

“…[7][8] Until now, the field of colloidal lithography has remained very active and increasingly complex structures have been-and are continued to be prepared in nanoscale dimensions, ranging from rings, discs and crescent-shaped particles to bowls, wells, or needles. [9][10] A plethora of applications have been demonstrated for colloidal lithography-based structure arrays that exploit different properties inherent to the process. The plasmonic properties of noble-metal nanoparticles have been extensively used to detect binding events; e.g.…”

“…[5] First reported by Fischer and Zingsheim in 1981, [4] colloidal lithography has matured into a widely-used technology and there are a number of reviews that highlight recent advances and developments. [9][10][122][123][124] The process flow of classical colloidal lithography is illustrated in Figure 3 Several years after the first report, Richard van Duyne and his group set out to explore scope and limitations of the fabrication process and investigated the intrinsic optical properties of such nanoscale metal particles (chapter 3.5). They used different metals and varied the size and shape of metal nanoparticle and managed to produce double and triple structures by multiple evaporation steps.…”