Direct Patterning of CsPbBr₃ Nanocrystals via Electron-Beam Lithography

Abstract

Lead-halide perovskite (LHP) nanocrystals have proven themselves as an interesting material platform due to their easy synthesis and compositional versatility, allowing for a tunable band gap, strong absorption, and high photoluminescence quantum yield (PLQY). This tunability and performance make LHP nanocrystals interesting for optoelectronic applications. Patterning active materials like these is a useful way to expand their tunability and applicability as it may allow more intricate designs that can improve efficiencies or increase functionality. Based on a technique for II–VI quantum dots, here we pattern colloidal LHP nanocrystals using electron-beam lithography (EBL). We create patterns of LHP nanocrystals on the order of 100s of nanometers to several microns and use these patterns to form intricate designs. The patterning mechanism is induced by ligand cross-linking, which binds adjacent nanocrystals together. We find that the luminescent properties are somewhat diminished after exposure, but that the structures are nonetheless still emissive. We believe that this is an interesting step toward patterning LHP nanocrystals at the nanoscale for device fabrication.

Review of metal-containing resists in electron beam lithography: perspectives for extreme ultraviolet patterning

“…Electron-beam-induced cross-linking of long-chain ligands (carboxylate and oleylamine) was also utilized for direct patterning of CsPbBr 3 nanocrystals. 188 This type of cross-linking is similar to what has been observed earlier in metal carboxylate-based resists (see section "Metal carboxylate-based resists").…”

“…Here upon exposure, oleic acid, the capping ligand for quantum dots, and a carboxylic acid, underwent cross-linking, rendering the exposed area insoluble in an apolar developer. Electron-beam-induced cross-linking of long-chain ligands (carboxylate and oleylamine) was also utilized for direct patterning of CsPbBr3 nanocrystals 188 . This type of cross-linking is similar to what has been observed earlier in metal carboxylate-based resists (see section “Metal carboxylate-based resists”).…”

Photocrosslinkable Zwitterionic Ligands for Perovskite Nanocrystals: Self‐Assembly and High‐Resolution Direct Patterning

“…[ 6–8 ] In line with these advances, facile routes to the direct patterning of the PNCs also need to be developed for practical applications and commercialization. [ 9–11 ] To precisely pattern PNCs, conventional photolithographic methods using UV, electron beam, and X‐ray have been attempted; [ 12–14 ] however, these approaches typically require high‐energy and time‐consuming processes or toxic chemicals. [ 15–17 ] Poor colloidal and structural stability is another obstacle considerably restricting the application of PNCs.…”

Ligand-Free Direct Optical Lithography of Bare Colloidal Nanocrystals via Photo-Oxidation of Surface Ions with Porosity Control

“…There are, accordingly, many well-developed methods for depositing NCs as patterned layers. These include inkjet printing, − electron-beam lithography, , transfer printing, nanoimprinting, and photolithography. − Each of these patterning techniques has its advantages and limitations in terms of cost, scalability, pattern resolution, and generality of approach. In assessing their capabilities, a priority lies in characterizing the surface chemical (ligand) environment of the NCs before and after patterning.…”