Low-Temperature Nanocrystal Unification through Rotations and Relaxations Probed by in Situ Transmission Electron Microscopy

Huis, Marijn A. van; Kunneman, Lucas T.; Overgaag, Karin; Xu, Qiang; Pandraud, G.; Zandbergen, H.W.; Vanmaekelbergh, Daniël

doi:10.1021/nl8024467

Cited by 178 publications

(214 citation statements)

References 26 publications

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“…Wellaligned fractured sections along the [1 1 1] orientation produces better efficiency, and vice versa. A similar mechanism was reported in PdSe nanocrystals [33,34].…”

Section: Factors That Facilitate Self-healingsupporting

confidence: 75%

Self-Healing of Fractured GaAs Nanowires

et al. 2011

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Molecular dynamics simulations are performed to investigate a spontaneous self-healing process in fractured GaAs nanowires with a zinc blende structure. The results show that such self-healing can indeed occur via rebonding of Ga and As atoms across the fracture surfaces, but it can be strongly influenced by several factors, including wire size, number of healing cycles, temperature, fracture morphology, oriented attachment and atomic diffusion. For example, it is found that the self-healing capacity is reduced by 46% as the lateral dimension of the wire increases from 2.3 to 9.2 nm, and by 64% after 24 repeated cycles of fracture and healing. Other factors influencing the self-healing behavior are also discussed.

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“…Wellaligned fractured sections along the [1 1 1] orientation produces better efficiency, and vice versa. A similar mechanism was reported in PdSe nanocrystals [33,34].…”

Section: Factors That Facilitate Self-healingsupporting

confidence: 75%

Self-Healing of Fractured GaAs Nanowires

et al. 2011

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“…Considering that the Pb-ribbons are positively charged while the Se-ribbons are negatively charged, the nanodomains induce tiny dipoles on the {111} surfaces, which will induce interactions between nanocrystallites. During a heating experiment of PbSe NCs, 15 experimental evidence was found for the existence of such nanodomains. Figure 5 shows a TEM image with a PbSe nanocrystal sticking out over the edge of a hole in the SiN membrane, with its {111} surface observed edge-on, at various instants in time.…”

Section: Resultsmentioning

confidence: 99%

“…However, at sufficiently short distance the interaction between the {111} multidomain surfaces might still be sufficiently strong to explain the dynamics or oriented attachment, reported in a previous work. 15 Although the calculations were performed only for uncapped surfaces, it is likely that nanodomain-patterning is also favorable for the case of capped {111} surfaces, considering that the interface energy is the sum of the formation energy of the surface and the adhesion energy of the surfactants. The formation energy of the PbSe surface is lower, while the nanodomains are still large enough in area to have strong interactions with the capping molecules.…”

Section: Resultsmentioning

confidence: 99%

Energetics of Polar and Nonpolar Facets of PbSe Nanocrystals from Theory and Experiment

et al. 2009

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M any chemical and physical processes and properties, such as crystal growth, crystal morphology, and adsorption, are controlled by the atomic structure of the surface and its energy. This is even more important for nanostructured materials, in which the surface energy gives a considerable contribution to the total energy. Knowledge of the surface structures and energies allows predicting and optimizing the synthesis and, eventually, processing of nanocrystals into genuine nanomaterials. In recent years, PbSe nanomaterials have been intensively studied because of their attractive physical properties and promises for near-infrared opto-electronic applications. 1Ϫ9 Through fusion of smaller nanocrystal units, larger nanostructures can be fabricated with a wide variety of single crystal morphologies, such as nanorods, spheres, cubes, stars, and rings. 1,10Ϫ15 The experiments suggest that the efficient oriented attachmentOthe mutual alignment of nanocrystals during or prior to fusionOcan be attributed to dipole interactions caused by the electrically charged, Pb-or Se-terminated {111} facets. 10,12Ϫ15 However, this is currently just a hypothesis. Although it is experimentally proven that the nanocrystals carry dipole moments, 16,17 the experiments are not sufficiently sophisticated to prove the presence of nonreconstructed, fully polar {111} facets, and theoretical investigations are absent.There are many experimental and theoretical studies on the properties of bulk PbSe, 18Ϫ22 while the literature on the surface structure and energy is scarce. Kimmura et al. 23 grew a PbSe {111} surface on the {111} surface of BaF 2 . From the results of the high-resolution Rutherford backscattering spectroscopy, they found that the PbSe {111} surface is dominated by Pb atoms.Moreels and co-workers prepared colloidal PbSe nanocrystals of a uniform size. 24 They also investigated the interplay between the Pb-coordinating ligands and the structure of the PbSe surfaces in solution by nuclear magnetic resonance spectroscopy (NMR). It was concluded that the ligands have a strong impact on the nanocrystal surfaces and that capped PbSe nanocrystals are nonstoichiometric with a surface that is composed mainly of oleic acid capped lead atoms. 24 Ma et al. investigated the geometric and electronic properties of PbX (X ϭ S, Se, and Te) {100} surfaces using the density functional method. 25 However, there is no information about the surface energies.With the fast increasing interest in colloidal semiconductor nanocrystals, it is of key importance to investigate the surface structures and related energies of colloidal PbSe

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“…Individual HNCs are still clearly visible, and we were not able to detect any sign of fusion, leading to their subsequent attachment. 61 Therefore, the changes observed in photoelectron spectroscopy only involve an internal transformation. Since we noticed similar effects on the evolution of the core level when the samples are annealed or are exposed to UV irradiation, the HNCs were studied with TEM where they could be annealed in situ and their transformation could be followed in real time.…”

Section: Discussionmentioning

confidence: 99%

Phase transformation of PbSe/CdSe nanocrystals from core-shell to Janus structure studied by photoemission spectroscopy

et al. 2013

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Photoelectron spectroscopic measurements have been performed, with synchrotron radiation on PbSe/CdSe heteronanocrystals that initially consist of core-shell structures. The study of the chemical states of the main elements in the nanocrystals shows a reproducible and progressive change in the valence-band and core-level spectra under photon irradiation, whatever the core and shell sizes are. Such chemical modifications are explained in light of transmission electron microscopy observations and reveal a phase transformation of the nanocrystals: The core-shell nanocrystals undergo a morphological change toward a Janus structure with the formation of semidetached PbSe and CdSe clusters. Photoelectron spectroscopy gives new insight into the reorganization of the ligands anchored at the surface of the nanocrystals and the modification of the electronic structure of these heteronanocrystals.

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Low-Temperature Nanocrystal Unification through Rotations and Relaxations Probed by in Situ Transmission Electron Microscopy

Cited by 178 publications

References 26 publications

Self-Healing of Fractured GaAs Nanowires

Self-Healing of Fractured GaAs Nanowires

Energetics of Polar and Nonpolar Facets of PbSe Nanocrystals from Theory and Experiment

Phase transformation of PbSe/CdSe nanocrystals from core-shell to Janus structure studied by photoemission spectroscopy

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