The Role of Liquid Ink Transport in the Direct Placement of Quantum Dot Emitters onto Sub‐Micrometer Antennas by Dip‐Pen Nanolithography

Abstract

Dip-pen nanolithography (DPN) is used to precisely position core/thick-shell ("giant") quantum dots (gQDs; ≥10 nm in diameter) exclusively on top of silicon nanodisk antennas (≈500 nm diameter pillars with a height of ≈200 nm), resulting in periodic arrays of hybrid nanostructures and demonstrating a facile integration strategy toward next-generation quantum light sources. A three-step reading-inking-writing approach is employed, where atomic force microscopy (AFM) images of the pre-patterned substrate topography are used as maps to direct accurate placement of nanocrystals. The DPN "ink" comprises gQDs suspended in a non-aqueous carrier solvent, o-dichlorobenzene. Systematic analyses of factors influencing deposition rate for this non-conventional DPN ink are described for flat substrates and used to establish the conditions required to achieve small (sub-500 nm) feature sizes, namely: dwell time, ink-substrate contact angle and ink volume. Finally, it is shown that the rate of solvent transport controls the feature size in which gQDs are found on the substrate, but also that the number and consistency of nanocrystals deposited depends on the stability of the gQD suspension. Overall, the results lay the groundwork for expanded use of nanocrystal liquid inks and DPN for fabrication of multi-component nanostructures that are challenging to create using traditional lithographic techniques.

Light-emitting metasurfaces

“…In a recent work [153], core/thick-shell "giant" nanocrystal quantum dots (gQDs) of various compositions were dispersed in a liquid ink, and a scanning probe tip was used to "write" small dots of the material onto silicon nanoantennas. High-resolution electro-hydrodynamic printing of QDs on plasmonic nanostructures with a few nanometer precision was also demonstrated [154].…”

All-Dielectric Resonant Meta-Optics Lightens up

“…Very recently, the defined integration of colloidal QDs with dielectric nanoresonators was also demonstrated using dippen lithography [34]. In this method, the QDs are first dispersed in an ink, which is then deposited onto the nanoresonators using an atomic force microscopy (AFM) tip.…”

Development of Dip‐Pen Nanolithography (DPN) and Its Derivatives

“…Thorough understanding and prediction of material transfer in DPN would be highly beneficial in regard to the homogeneity of the lithography outcome . This would be crucial in the context of using DPN in industrial fabrication applications, but—as detailed above—is still not fully achieved (especially in regard to the liquid inks for their even more complicated transfer theory).…”