Revealing Grain Boundaries and Defect Formation in Nanocrystal Superlattices by Nanodiffraction

TL;DR

This study uses nanodiffraction to investigate how grain boundaries and defects form in nanocrystal superlattices, revealing stress release mechanisms and the importance of substrate interactions for large domain sizes.

Contribution

It demonstrates how nanodiffraction can reveal detailed structural changes at grain boundaries in nanocrystal superlattices, highlighting the role of substrate interactions in domain growth.

Findings

Lattice constant decreases near grain boundaries

Superlattice undergoes out-of-plane rotation at boundaries

Correlations between nanocrystals survive structural changes

Abstract

X-ray nanodiffraction is applied to study the formation and correlation of domain boundaries in mesocrystalline superlattices of PbS nanocrystals with face-centered cubic structure. Each domain of the superlattice can be described with one of two mesocrystalline polymorphs with different orientational order. Close to a grain boundary, the lattice constant decreases and the superlattice undergoes an out-of-plane rotation, while the orientation of the nanocrystals with respect to the superlattice remains unchanged. These findings are explained with the release of stress on the expense of specific nanocrystal-substrate interactions. The fact that correlations between adjacent nanocrystals are found to survive the structural changes at most grain boundaries implies that the key to nanocrystal superlattices with macroscopic domain sizes are strengthened interactions with the substrate.