Atomic Lattice Resolved Electron Tomography of a 3D Self-Assembled Mesocrystal

摘要

Complex 3D architectures of nanoscale building blocks can be created by selfassembly,but characterization of the atomic to mesoscale structure of suchmaterials is limited by the difficulty of visualizing atoms across multiple lengthscales. Here, scanning transmission electron microscopy (STEM) and full-tilttomographic reconstruction are used to image a single-crystalline region ofa 3D epitaxially-fused PbSe quantum dot (QD) superlattice containing 633 QDsat a spatial resolution of 2.16 ?. The combined real-space and reciprocal-spaceanalysis enables 3D mesoscale correlations of atomic lattice and superlatticeorder across hundreds of nanocrystals in 3D for the first time. Inhomogeneityin QD positional and orientational order reveals that the QD surface layerstemplate the superlattice and that orientational entropy is higher in the interiorlayers than the surface layers. The measurement and analysis techniques presentedhere are applicable to a broad range of 3D nanostructured materials.