Site-Specific Colloidal Crystal Nucleation by Template-enhanced Particle Transport

TL;DR

This study introduces a novel template design with moire patterns that directs colloidal crystal nucleation and growth, overcoming mobility limitations and enabling precise control over surface architecture at the single-particle level.

Contribution

It presents a new approach using spatially varying templates to control colloidal nucleation and growth, extending template-assisted techniques to colloids with limited surface mobility.

Findings

Achieved high-fidelity nucleation control on colloidal surfaces.

Demonstrated direct observation of nucleation and growth kinetics.

Enabled fabrication of complex colloidal surface architectures.

Abstract

The monomer surface mobility is the single most important parameter that decides the nucleation density and morphology of islands during thin film growth. During template-assisted surface growth in particular, low surface mobilities can prevent monomers from reaching target sites and this results in a partial to complete loss of nucleation control. While in atomic systems a broad range of surface mobilities can be readily accessed, for colloids, owing to their large size, this window is substantially narrow and therefore imposes severe restrictions in extending template-assisted growth techniques to steer their self-assembly. Here, we circumvented this fundamental limitation by designing templates with spatially varying feature sizes, in this case moire patterns, which in the presence of short-range depletion attraction presented surface energy gradients for the diffusing colloids. The templates serve a dual purpose, first, directing the particles to target sites by enhancing their surface mean free paths and second, dictating the size and symmetry of the growing crystallites. Using optical microscopy, we directly followed the nucleation and growth kinetics of colloidal islands on these surfaces at the single-particle level. We demonstrate nucleation control, with high fidelity, in a regime that has remained unaccessed in theoretical, numerical and experimental studies on atoms and molecules as well. Our findings pave the way for fabricating non-trivial surface architectures composed of complex colloids and nanoparticles.