Fabrication of Nearly‐Hyperuniform Substrates by Tailored Disorder for Photonic Applications

Abstract

lithography, provide great flexibility but are slow and expensive, and are therefore not feasible. Conventional scalable techniques, for instance random etching processes such as chemical wet etching [3,4] or plasma dry etching, [5,6] operate in a small window of parameters, thus offering only limited freedom of design and the statistics of fabricated disordered interfaces is more or less fixed. Bottom up, self-organized colloid deposition is a promising candidate for scalable interface texturing. [7][8][9] There are a number of both theoretical and experimental studies on how structures fabricated by colloid deposition can be used for light management in photo nic devices such as solar cells. [10][11][12][13][14][15] Colloid-defined samples are mostly used to produce strictly periodic structures, such as hexagonal photonic crystals and nanoparticle arrays. [7][8][9] However, partly ordered and disordered structures have been shown to possibly perform significantly better than perfectly ordered structures in recent studies. [15][16][17][18][19][20] Nevertheless, a colloid-based deposition technique to prepare disordered structures with the ability to tailor its topographical statistics, and thus a tailored optical response, is still missing.In this work, we investigate the scalable deposition of disordered arrangements of colloidal nanoparticles that selforganize on a substrate to create disordered topographies of defined statistics. The fabricated substrates may serve as templates in a subsequent fabrication process, e.g., etching, nanosphere lithography, or overcoating with optical materials such as absorber layers for solar cells or light generation layers for solid-state lighting. Irregular deposition of colloids is often governed by unwanted effects, such as ordering into regular periodic patterns, autostratification, or separation of particle sizes due to surface tension or depletion forces. [9,[21][22][23][24] Here, we introduce a self-stabilized particle deposition process to overcome these effects. The process allows us to control lateral and vertical structure dimensions by setting size distribution and interparticle spacing of a sub-monolayer of particles through experimentally easy-to-access parameters. By understanding the deposition process and the resulting statistics, we can predict the topography and thereby enable optimization of these structures for a specific application without the need for laborious trial-and-error experiments.The pattern structure of the substrates fabricated by our procedure is of correlated disorder and reveals features that resemble hyperuniformity. [25,26] Like glasses, disorderd Disordered optical substrates play a key role in photonic applications. Furthermore, structures of correlated, in particular hyperuniform, disorder are an emerging new class of photonic material enabling new ways of k-space engineering. Yet, there are little to no feasible technologies that allow fabrication of tailored disordered structures to facilitate a tailored optical response. This work ...

Enhanced absorption of waves in stealth hyperuniform disordered media

“…Robustness to positional variations of the scatterers is also expected, since random displacements do not seem to destroy hyperuniformity [48]. Together with the development of selfassembly processes able to produce hyperuniform architectures [49,50], the results in this article could guide the design of disordered correlated materials with blackbodylike absorption. The results should apply to all kinds of waves propagating in materials made of subwavelength absorbing scatterers in a non-absorbing host medium.…”

Tailored Light Scattering through Hyperuniform Disorder in Self‐Organized Arrays of High‐Index Nanodisks

“…Disk positions were extracted from images of 104 × 70 μm 2 area via template matching, corresponding to about 2.000 Disks for the uncorrelated pattern and 16.000 for the most dense. [ 33,62 ] Briefly, the image of a sample particle was scanned over the original SEM image and tested for similarity at every point. Some disk pairs exhibit nominal surface‐to‐surface distances ≤0 nm (see e.g., Figure 3g) due to slight merging of the PMMA particles during tempering.…”

Over 65% sunlight absorption in a 1 μm Si slab with hyperuniform texture

“…For instance, it has been shown that the structure factor of dispersed colloidal particle (e.g. beads) patterns can be tuned by the ionic strength of the particular solvent 65,66 and that the dewetting of semiconductor layers leads to HUD patterns. 67 Also, soft-imprint conformal lithography has proven an excellent low-cost alternative to pattern large-areas with a resolution below 10 nm that could actually serve for both HUD holes and HUD network.…”