Polarity continuation and frustration in ZnSe nanospirals

Li, Luying; Tu, Fanfan; Jin, Lei; Choy, Wallace C. H.; Gao, Yihua; Wang, Jianbo

doi:10.1038/srep07447

Cited by 8 publications

(8 citation statements)

References 29 publications

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“…As evident from the normal WZ ZnSe shown in Figure a, the projected orientation of the Zn–Se bonds in the horizontal direction are reversed in alternating rows along the c -axis (indicated by red and green arrows). This orientation indicates that the spontaneous polarization is aligned with the c -direction, without a component in the ab plane, and corresponds to its polarized space group P 63 mc . , In our case, however, we observe an unusual symmetry-breaking structure and polarization phenomenon with the WZ ZnSe NCs. Figure b is the HAADF image of a typical WZ ZnSe particle that contains defective segments.…”

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confidence: 42%

“…As a typical representative of II–VI semiconductor NCs, ZnSe possesses structures that include zincblende (ZB), with cubic stacking in the [111] direction, and wurtzite (WZ), with hexagonal stacking in the [0001] direction. − ZB ZnSe is thermodynamically stable, whereas WZ ZnSe is metastable. In comparison with ZB ZnSe, WZ ZnSe is difficult to prepare under mild reaction conditions. , Furthermore, the controlled growth of WZ ZnSe NCs with alternating Zn and Se atom arrangements leads to a localized excess of charge, which is due to the polarization associated with symmetry-breaking structures. ,, The accumulation of charge in the WZ ZnSe structure can also affect the electron–hole recombination statistics, which may result in new properties. , Here, we propose WZ ZnSe as an ideal model to investigate the relationship between the WZ ZnSe structure and its ECL behavior.…”

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confidence: 99%

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Electrochemiluminescence Tuned by Electron–Hole Recombination from Symmetry-Breaking in Wurtzite ZnSe

et al. 2016

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The research of highly active electrochemiluminescence (ECL) materials with low toxicity and good solubility remains a substantial challenge. In this work, we present a synthesis method to prepare soluble wurtzite (WZ) ZnSe nanocrystals (NCs), which exhibit good ECL properties. Using high-angle annular-dark-field imaging together with electron hologram methods, we observe that the WZ ZnSe NCs exhibit an unusual symmetry-breaking phenomenon, where the translational symmetry of the polarized Zn-Se bond is broken. The formation of a symmetry-breaking region leads to an accumulation of charge. The good ECL response originates from the increased efficiency of electron-hole recombination by the excess charge redistribution in WZ ZnSe NCs. This study of the relationship between ECL behavior and the architecture of NCs suggests that careful control over the NC structures of semiconductors can tailor their charge distribution via symmetry breaking, which opens new avenues for the design of novel classes of agents for optoelectronic applications.

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confidence: 99%

Electrochemiluminescence Tuned by Electron–Hole Recombination from Symmetry-Breaking in Wurtzite ZnSe

et al. 2016

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“…The HAADF–STEM image intensity directly scales with the atomic number Z giving Z contrast . In previous studies, the aberration‐corrected HAADF–STEM technique has been applied to characterization of local faulted structures as well as analysis of related structure–property relations at atomic resolution. Figure c is HAADF–STEM image of a small piece of K x WO 3 nanosheet with growth direction along [0001].…”

Section: Resultsmentioning

confidence: 99%

Atomic‐Scale Study of Cation Ordering in Potassium Tungsten Bronze Nanosheets

Jiang

et al. 2017

Advanced Science

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It has long been accepted that the formation of superlattices in hexagonal‐based potassium tungsten bronzes is attributed to K vacancies only, together with small displacements of W cations. Here, the superlattices within potassium tungsten bronze nanosheets both structurally and spectroscopically at atomic resolution using comprehensive transmission electron microscopy techniques are studied. The multidimensional chemical analyses are realized by energy‐dispersive X‐ray spectroscopy, electron energy‐loss spectroscopy, and X‐ray photoelectron spectroscopy, the atomic‐scale structures are characterized using aberration‐corrected scanning transmission electron microscopy with high‐angle annular‐dark‐field detector. The observed superstructures are mainly attributed to small amount of W vacancies within single atomic layer, which would recover to more uniform distributions of W vacancies with lower concentrations at higher temperature. The band regions of different orientation from the matrix tend to regulate the superstructures to be pinned along the same direction, forming domains of highly ordered structures. The characterization of cation ordering and recovery processes of nanostructures from chemical and structural point of view at atomic resolution enables rational design of optoelectronic devices with controlled physical properties.

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“…found that wurtzite ZnSe nanocrystals possess defective segments that break the translational symmetry of the crystal, as illustrated by aberration‐corrected high‐angle annular‐dark‐field (HAADF) images of wurtzite ZnSe nanocrystals in Figure 14. Such symmetry‐breaking defects induce local charge imbalances within the material, and result in novel optical properties [122,124] . Zinc blende ZnSe nanocrystals also displayed symmetry‐breaking defects, although electron holography experiments revealed that the net local charges in defective segments of ZnSe nanocrystals were greater in the wurtzite phase than in the zinc blende phase [122] …”

Section: Properties and Applications Of Semiconductor Nanocrystals Wimentioning

confidence: 99%

Polymorphic Metastability in Colloidal Semiconductor Nanocrystals

Tappan

Brutchey

2020

ChemNanoMat

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Metastable polymorphs of inorganic solids often possess material properties not present in the corresponding thermodynamic polymorphs, making them targets for the development of new functional materials. In contrast with isolating metastable bulk materials, syntheses of metastable polymorphs on the nanoscale are aided by fast non‐equilibrium reaction kinetics and the favorable thermodynamic influence of surface energies, giving rise to greater ease of access to metastable high‐temperature polymorphs and, in some cases, new polymorphs that do not exist in the bulk. The syntheses of metastable semiconductor nanocrystals are of interest for their potentially unique optoelectronic and physicochemical properties. However, in many material systems, synthesizing nanocrystalline products away from thermodynamic equilibrium in a predictable manner remains an outstanding challenge. This review outlines direct synthetic methodologies that have been developed to enable control over the nucleation and growth of metastable polymorphs of semiconductor nanocrystals by tailoring reaction conditions, precursor kinetics, ligand and surface effects, and other synthetic levers. The case studies reviewed herein expound on the direct syntheses of metastable ZnSe, Cu2SnSe3, CuInSe2, Ag2Se, and AgInSe2 nanocrystals, and although there remain numerous examples of metastable nanocrystal syntheses outside of these metal chalcogenide systems, the concepts discussed are of general utility to the field of metastable nanocrystal syntheses as a whole. Explicit examples in which new functional properties are afforded by metastable polymorphs of the aforementioned material systems are presented within the context of applications for solar cells, photonics, and optical sensing. Finally, the factors that affect the kinetic persistence of metastable nanocrystalline polymorphs are discussed at length for these material systems.

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Polarity continuation and frustration in ZnSe nanospirals

Cited by 8 publications

References 29 publications

Electrochemiluminescence Tuned by Electron–Hole Recombination from Symmetry-Breaking in Wurtzite ZnSe

Electrochemiluminescence Tuned by Electron–Hole Recombination from Symmetry-Breaking in Wurtzite ZnSe

Atomic‐Scale Study of Cation Ordering in Potassium Tungsten Bronze Nanosheets

Polymorphic Metastability in Colloidal Semiconductor Nanocrystals

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