Mechanistic Insights into Superlattice Transformation at a Single Nanocrystal Level Using Nanobeam Electron Diffraction

daSilva, Jessica Cimada; Smeaton, Michelle A.; Dunbar, Tyler; Xu, Yuanze; Balazs, Daniel M.; Kourkoutis, Lena F.; Hanrath, Tobias

doi:10.1021/acs.nanolett.0c01579

Cited by 23 publications

(56 citation statements)

References 32 publications

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“…In this case, we can leverage the diversity of ligand-separated nanocrystal superlattices to achieve attached nanocrystal superlattice structures. In the case of PbX assembly and attachment, the initial ligand-separated nanocrystals typically adopt a hexatic phase and, in the case of monolayers, typically transform to a square superlattice upon attachment . This requires concerted shuffling of nanocrystals, and the kinetics of this process must be carefully controlled to achieve well-ordered square superlattices.…”

Section: Results and Discussionmentioning

confidence: 99%

“…In the case of PbX assembly and attachment, the initial ligand separated nanocrystals typically adopt a hexatic phase, and, in the case of monolayers, typically transform to a square superlattice upon attachment. 43 This requires concerted shuffling of nanocrystals, and the kinetics of this process must be carefully controlled to achieve well-ordered square superlattices. Indeed this complex interplay results in a diversity of structures including residual hexatic order, 44 distorted square superlattices, 43 or in the case of bi-layers more complex silicene structures.…”

Section: Comparison Of Nc Assembly/silar Attachment With Direct Atomic Attachmentmentioning

confidence: 99%

“…43 This requires concerted shuffling of nanocrystals, and the kinetics of this process must be carefully controlled to achieve well-ordered square superlattices. Indeed this complex interplay results in a diversity of structures including residual hexatic order, 44 distorted square superlattices, 43 or in the case of bi-layers more complex silicene structures. 45 Indeed the structural diversity as a result of small tweaks to direct attachment of PbX is intriguing and has potential to yield diverse structures.…”

Section: Comparison Of Nc Assembly/silar Attachment With Direct Atomic Attachmentmentioning

confidence: 99%

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Colloidal Synthesis Path to 2D Crystalline Quantum Dot Superlattices

et al. 2020

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By combining colloidal nanocrystal synthesis, self assembly, and solution phase epitaxial growth techniques, we developed a general method for preparing single dot thick atomically attached quantum dot (QD) superlattices with high quality translational and crystallographic orientational order along with state-of-the-art uniformity 1 in the attachment thickness. The procedure begins with colloidal synthesis of hexagonal prism shaped core/shell QDs (e.g. CdSe/CdS), followed by liquid subphase selfassembly and immobilization of superlattices on a substrate. Solution phase epitaxial growth of additional semiconductor material fills in the voids between the particles resulting in a QD-in-matrix structure. The photoluminescence emission spectra of the QD-in-matrix structure retains characteristic 0D electronic confinement. Importantly, annealing of the resulting structures removes inhomogeneities in the QD-QD inorganic bridges, which our atomistic electronic structure calculations demonstrate would otherwise lead to Anderson-type localization. The piece-wise nature of this procedure allows one to independently tune the size and material of the QD core, shell, QD-QD distance, and the matrix material. These four choices can be tuned to control many properties (e.g. degree of quantum confinement, quantum coupling, band alignments, etc.) depending on the specific applications. Finally, cation exchange reactions can be performed on the final QD-in-matrix, as demonstrated herein with a CdSe/CdS to HgSe/HgS conversion.

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Section: Results and Discussionmentioning

confidence: 99%

Section: Comparison Of Nc Assembly/silar Attachment With Direct Atomic Attachmentmentioning

confidence: 99%

Section: Comparison Of Nc Assembly/silar Attachment With Direct Atomic Attachmentmentioning

confidence: 99%

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Colloidal Synthesis Path to 2D Crystalline Quantum Dot Superlattices

et al. 2020

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“…However, on the basis of our previously reported work using nanobeam diffraction mapping with 4D-STEM, we expect that most rotations are less than six degrees. 28 Rotation of a QD to match the crystallographic orientation of one of its neighbors can then enable formation of a new connection between them.…”

Section: Resultsmentioning

confidence: 99%

Mapping Defect Relaxation in Quantum Dot Solids upon In Situ Heating

et al. 2021

Self Cite

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Epitaxially connected quantum dot solids have emerged as an interesting class of quantum confined materials with the potential for highly tunable electronic structures. Realization of the predicted emergent electronic properties has remained elusive due in part to defective interdot epitaxial connections. Thermal annealing has shown potential to eliminate such defects, but a direct understanding of this mechanism hinges on determining the nature of defects in the connections and how they respond to heating. Here, we use in situ heating in the scanning transmission electron microscope to probe the effect of heating on distinct defect types. We apply a real space, local strain mapping technique, which allows us to identify tensile and shear strain in the atomic lattice, highlighting tensile, shear, and bending defects in interdot connections. We also track the out-of-plane orientation of individual QDs and infer the prevalence of out-of-plane twisting and bending defects as a function of annealing. We find that tensile and shear defects are fully relaxed upon mild thermal annealing, while bending defects persist. Additionally, out-of-plane orientation tracking reveals an increase in correctly oriented QDs, pointing to a relaxation of either twisting defects or out-of-plane bending defects. While bending defects remain, highlighting the need for further study of orientational ordering during the preattachment phase of superlattice formation, these atomic-scale insights show that annealing can effectively eliminate tensile and shear defects, a promising step toward delocalization of charge carriers and tunable electronic properties.

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“…Specifically, the precise position and atomic lattice (AL) orientation (in plane and out of plane) of nearly all ≈300 NPs in the field of view could be deduced. [ 193 ] Based on the data, the authors could show that the assembly and transformation of PbS NP monolayers on ethylene glycol proceeds via a pre‐aligned (〈11n〉 AL || 〈11〉 SL ) hexatic into the final square lattice in which the alignment AL‐SL is further optimized. The transformation was induced by injecting ethylene diamine into the liquid subphase.…”

Section: Characterization Of Nps Assemblies and Supercrystalsmentioning

confidence: 99%

Recent Notable Approaches to Study Self‐Assembly of Nanoparticles with X‐Ray Scattering and Electron Microscopy

Schulz

Lokteva

Parak

et al. 2021

Part & Part Syst Charact

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several issues far from being resolved: for many systems long-range periodic order is not routinely achieved, reproducibility is often not optimal and truly emergent and new properties arising from the supercrystal formation could be demonstrated for just a few systems. [3][4][5][6][7] From the materials science perspective there is no established figure of merit or common set of parameters allowing to quantify "quality" of NP superlattices and supercrystals. In lieu of such standard procedures, terms as well-ordered, crystalline order, quasicrystalline, etc., are usually used in literature. However, there exist no commonly accepted definitions of what qualifies, e.g., as "well-ordered."In this review, we want to highlight some recent experimental developments and new approaches to study self-assembly of NPs or structure formation of NP supercrystals and their final structure. We focus on NP, the broad field of photonic materials prepared by self-assembly of larger colloidal particles is not covered herein. [8][9][10] The introduction of the basic concepts of NP self-assembly will be kept short and should be considered as an overview, for more background and details excellent comprehensive reviews are available. [2,11] We will then briefly address and discuss the expectations associated with self-assembled materials, especially the proposed emergence of new properties directly related to order. In the second part of the review, we will present recent innovative approaches for the investigation of self-assembly and self-assembled structures that go beyond the standard characterization. We focus mainly on structure and structure formation and less on properties, so most of the studies are based on scattering and electron microscopy. Figure 1 provides an overview roughly following this outline. Self-Assembly of NanoparticlesSelf-assembly is a broad term and occurs on all scales from atoms, ions, and molecules to galaxies, as pointed out by Whitesides and Grzybowski. [12] It can be defined as the autonomous organization of multiple discrete components into ordered structures, driven by energetics or entropy or both. [2,13] In nature, countless examples of highly complex and functional structures resulting from self-assembly can be found, Self-assembly of nanoparticles (NPs) has evolved into a powerful tool for the synthesis of superstructures with tailored properties. The quality, diversity, and complexity of synthesized structures are continuously improving and fascinating new collective properties are demonstrated. At the same time, the rapid development of electron microscopy and synchrotron sources for X-rays has enabled new exciting experimental approaches to study structure and structure formation in the context of NP self-assembly. In this review, some recent studies and what can be learned from them are highlighted and discussed. It is started with a general introduction covering important concepts, experimental approaches, commonly obtained structures, the ideas of artificial atoms, and emerging properties a...

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Mechanistic Insights into Superlattice Transformation at a Single Nanocrystal Level Using Nanobeam Electron Diffraction

Cited by 23 publications

References 32 publications

Colloidal Synthesis Path to 2D Crystalline Quantum Dot Superlattices

Colloidal Synthesis Path to 2D Crystalline Quantum Dot Superlattices

Mapping Defect Relaxation in Quantum Dot Solids upon In Situ Heating

Recent Notable Approaches to Study Self‐Assembly of Nanoparticles with X‐Ray Scattering and Electron Microscopy

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