Resilient Pathways to Atomic Attachment of Quantum Dot Dimers and Artificial Solids from Faceted CdSe Quantum Dot Building Blocks

Abstract

The goal of this work is to identify favored pathways for preparation of defect resilient attached wurtzite CdX (X = S, Se, Te) nanocrystals. We seek guidelines for oriented attachment of faceted nanocrystals that are most likely to yield pairs of nanocrystals with either few or no electronic defects, or electronic defects that are in and of themselves desirable and stable. Using a combination of in-situ high resolution transmission electron microscopy (HRTEM) and electronic structure calculations, we evaluate the relative merits of atomic attachment of wurtzite CdSe nanocrystals on the {11 � 00} or {112 � 0} family of facets. Pairwise attachment on either facet can lead to perfect interfaces, provided the nanocrystal facets are perfectly flat and the angles between the nanocrystals can adjust during the assembly. Considering defective attachment, we observe for {11 � 00} facet attachment that only one type of edge dislocation forms, creating deep hole traps. For {112 � 0} facet attachment, we observe that four distinct types of dislocations form, some of which lead to deep hole traps while others only to shallow hole traps. HRTEM movies of the dislocation dynamics show that dislocations at {11 � 00} interfaces can be removed, albeit slowly. Whereas only some extended dislocations at {112 � 0} interfaces could be removed, others were trapped at the interface. Based on these insights, we identify the most resilient pathways to atomic attachment of pairs of wurtzite CdX nanocrystals and consider how these insights can translate to creation of electronically useful materials from quantum dots with other crystal structures.

Colloidal Synthesis Path to 2D Crystalline Quantum Dot Superlattices

“…electron and hole) states using the semi-empirical pseudopotential method 36 and filter-diagonalization techniques, 35,56 as discussed in detail previously. 24 Atomic models with corresponding carrier densities were rendered using VESTA. 57…”

Simulations of nonradiative processes in semiconductor nanocrystals

“…Furthermore, these continuum models are, by nature, blind to atomistic detail, such as defects, strain at heterostructure interfaces, and facet-dependent properties. 91,92 Our approach is based on the semiempirical pseudopotential method, 9,26,73 which was first developed to characterize the band structures of simple bulk materials 23 and was later extended to describe the role of surfaces 93 and confinement. 9,24 The basic assumption made is that the bulk band structure can be described by a simple, non-interacting model Hamiltonian…”

Semiconductor Bow‐Tie Nanoantenna from Coupled Colloidal Quantum Dot Molecules

“…Thes trength of the nanocrystals chemistry approach is based on the utilization of the highly developed CQDs as building blocks with well-controlled crystal lattice,s ize and shape that can be assembled to complex architectures via control of their surface chemistry. [15] In particular,f using the adjacent CQD building blocks has been utilized to form arrays, [16,17] honeycomb superlattices, [18] elongated coupled hetero-structures, [19] and artificial dimer molecules. [20] Such epitaxial fusion of spherical core/shell nanocrystals with wurtzite crystal lattice,y ielded homodimer molecules where quantum mechanical tunneling facilitated electron wavefunction hybridization between the two adjacent CQDs.B y utilizing the colloidal approach for the controlled adjunction of tetrahedral quantum dots with zinc-blende crystal lattice we achieve the desired bow-tie nanoantenna architecture.…”