Growth and Morphology of PbSe Mesocrystals

This work describes the growth, (surface) morphology, and defect structure of mesocrystals composed of lead selenide (PbSe) nanocrystals enveloped by a corona of oleate ligands. Three crystal growth methods are explored to reproducibly obtain mesocrystals up to tens of micrometers in size. The best results are obtained by vapor in-diffusion of a suited antisolvent into a PbSe nanocrystal suspension. This yields octahedral and trigon-shaped cubic close-packed (fcc) crystals composed of partially oriented nanocrystals. The morphology and surface structure of the mesocrystals are investigated by scanning electron microscopy and atomic force microscopy. This reveals a wealth of features, including various kinds of single and multiple {1 1 1} twinning, monolayer, and multilayer growth steps, the lower ones often being undulated by impurity blocking, ⟨1 2 1⟩ and ⟨1 1 0⟩ striations formed by a postgrowth phase transformation, linear growth faults, slip lines, and cracks. These observations show that the growth and defect structure of PbSe mesocrystals, for the most part, follow the classical crystal growth concepts, which are based on molecular or atomic growth units. The absence of spiral growth is a notable exception.