Fig. 2: Impact of inorganic ZnF2 on the shell morphology of large InAs/InP/ZnSe/ZnS core/multishell QDs.
From: Efficient and stable near-infrared InAs quantum dot light-emitting diodes
a Schematic illustrating ZnSe shell growth during synthesis without ZnF2 (top) and with ZnF2 (bottom). b, c STEM and HRTEM images of QDs synthesized without ZnF2. d, e STEM and HRTEM images of QDs synthesized with ZnF2. The inset in (d) shows the corresponding energy dispersive spectroscopy (EDS) elemental mapping of In (yellow) and Zn (purple). The scale bars in the STEM and HRTEM images and the EDS mapping inset are 20 nm, 5 nm, and 5 nm, respectively. f, g Interfacial energies of the {100}, {111}, and {110} facets using a slab model consisting of an InAs substrate with a single epitaxial ZnSe monolayer as a function of ligand coverage: f without fluoride species and g with one original ligand replaced by F or HF. h Binding energies (Eb) of various species on the {100}, {111} and {110} facets at optimal ligand coverage. i Schematic diagram depicting preferential ZnSe growth on the {111} facet without ZnF2, leading to anisotropic morphology. j Schematic diagram of QD growth with ZnF2 illustrating the critical role of fluoride species in reducing growth rate differences across the three facets and thus promoting isotropic ZnSe shell growth. The gray, yellow, light blue, orange, dark purple, cyan, navy blue, and black spheres represent the elements In, As, P, Zn, Se, F, O, and C, respectively.
