On the selective formation of cubic tetrastack crystals from tetravalent patchy particles

TL;DR

This study demonstrates that tetravalent patchy particles can selectively self-assemble into cubic tetrastack crystals, with external fields enhancing crystal quality and controlling growth mechanisms, relevant for photonic applications.

Contribution

It reveals how external fields influence the selective formation and epitaxial growth of cubic tetrastack crystals from patchy particles, a novel insight into directed self-assembly.

Findings

External fields enable formation of defect-free single crystals.

Surface-induced ordering improves crystal quality over bulk formation.

Stronger external fields promote layered growth and better crystal order.

Abstract

Achieving the formation of target open crystalline lattices from colloidal particles is of paramount importance for their potential application in photonics. Examples of such desired structures are the diamond, tetrastack, and pyrochlore lattices. Here, we demonstrate that the self-assembly of tetravalent patchy particles results in the selective formation of cubic tetrastack crystals, both in the bulk and in the systems subjected to external fields exerted by the solid substrate. It is demonstrated that the presence of an external field allows for the formation of well-defined single crystals with a low density of defects. Moreover, depending on the strength of the applied external field, the mechanism of epitaxial growth changes. For weakly attractive external fields, the crystallization occurs in a similar manner as in the bulk, since the fluid does not wet the substrate. Nonetheless, the formed crystal is considerably better ordered than the crystals formed in bulk, since the surface induces the ordering in the first layer. On the other hand, it is demonstrated that the formation of well-ordered cubic tetrastack crystals is considerably enhanced by the increase in external field strength, and the formation of the thick crystalline film occurs via a series of layering transitions.