Single-defect phonons imaged by electron microscopy

Yan, Xingxu; Liu, Chengyan; Gadre, Chaitanya; Gu, Li; Aoki, Toshihiro; Lovejoy, Tracy C.; Dellby, Niklas; Krivanek, Ondrej L.; Schlom, D. G.; Wu, Ruqian; Pan, Xiaoqing

doi:10.1038/s41586-020-03049-y

Cited by 139 publications

(127 citation statements)

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“…A wide range of imaging and diffraction techniques provide unique information about the crystal structure of the studied samples, such as the local elemental composition, electronic structure and bonding down to the atomic level [1]. Thanks to the latest developments, not only has the resolution limit been pushed below 0.5 Å, but nowadays even the behavior of materials and devices at the atomic scale can be mapped [2,3]. TEM is practically an indispensable technique for investigating crystal defects and studying phase transitions.…”

Section: Introductionmentioning

confidence: 99%

Diffraction Features from (101¯4) Calcite Twins Mimicking Crystallographic Ordering

Németh

2021

Minerals

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During phase transitions the ordering of cations and/or anions along specific crystallographic directions can take place. As a result, extra reflections may occur in diffraction patterns, which can indicate cell doubling and the reduction of the crystallographic symmetry. However, similar features may also arise from twinning. Here the nanostructures of a glendonite, a calcite (CaCO3) pseudomorph after ikaite (CaCO3·6H2O), from Victoria Cave (Russia) were studied using transmission electron microscopy (TEM). This paper demonstrates the occurrence of extra reflections at positions halfway between the Bragg reflections of calcite in 0kl electron diffraction patterns and the doubling of d104 spacings (corresponding to 2∙3.03 Å) in high-resolution TEM images. Interestingly, these diffraction features match with the so-called carbonate c-type reflections, which are associated with Mg and Ca ordering, a phenomenon that cannot occur in pure calcite. TEM and crystallographic analysis suggests that, in fact, (101¯4) calcite twins and the orientation change of CO3 groups across the twin interface are responsible for the extra reflections.

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Section: Introductionmentioning

confidence: 99%

Diffraction Features from (101¯4) Calcite Twins Mimicking Crystallographic Ordering

Németh

2021

Minerals

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“…It is generally believed that the phonons-defect interaction plays a decisive role in thermal conductivity, especially when the material's dimension is reduced to the nanoscale. [138] Aerogels are solid materials with 3D nanoporous structure. Therefore, the scattering of phonons by the solid-solid or solid-gas interfaces in an aerogel structure will reduce the contribution of λ sc to thermal conductivity.…”

Section: Thermal Conductivity In Aerogelsmentioning

confidence: 99%

Recent advances in novel aerogels through the hybrid aggregation of inorganic nanomaterials and polymeric fibers for thermal insulation

et al. 2021

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Aerogel is a nanoporous solid material with ultrahigh porosity, ultralow density, and thermal conductivity, which is considered to be one of the most promising high‐performance insulation materials today. However, traditional pure inorganic aerogels (i.e., silica aerogel) exhibit inherent structural brittleness, making their processing and handling difficult, and their manufacturing costs are relatively high, which limits their large‐scale practical use. The recently developed aerogel based on polymer nanofibers has ultralow thermal conductivity and density, excellent elasticity, and designable multifunction. More importantly, one‐dimensional polymer nanofibers are directly used as building blocks to construct the network of aerogels via a gelation‐free process. This greatly simplifies the aerogel preparation process, thereby bringing opportunities for large‐scale aerogel applications. The aggregation of inorganic nanomaterials and polymer nanofibers is considered to be a very attractive strategy for obtaining highly flexible, easily available, and multifunctional composite aerogels. Therefore, this review summarizes the recent advances in novel aerogels through the hybrid aggregation of inorganic nanomaterials and polymeric fibers for thermal insulation. The main processing routes, porous microstructure, mechanical properties, and thermal properties and applications of these aerogels are highlighted. In addition, various future challenges faced by these aerogels in thermal insulation applications are discussed in this review.

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“…Additionally, by varying the convergence semi-angle (α) and EELS collection geometry, momentum resolution is achieved, enabling angle-resolved vibrational spectroscopy that maps out the phonon dispersion relations [3]. Balancing these three aspects: spatial, energy, and momentum resolutions, we can obtain a powerful space-and angle-resolved vibrational spectroscopy to investigate local phonon modes near the crystalline defects in semiconductors and their heterostructures [4]. Planar defects such as stacking faults and interfaces are believed to impede phonon propagation and modify the vibrational structure [5].…”

mentioning

confidence: 99%

“…The increased width can be explained by the penetration of the defect phonon modes into the surrounding SiC region. Both the reduced phonon energy and flattened dispersion curves of defect phonon modes help understand the defect-induced reduction of thermal conductivity [4].…”

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confidence: 99%

Space- and Angle-Resolved Vibrational Spectroscopy to Probe the Local Phonon Modes at Planar Defects

et al. 2021

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Single-defect phonons imaged by electron microscopy

Cited by 139 publications

References 49 publications

Diffraction Features from (101¯4) Calcite Twins Mimicking Crystallographic Ordering

Diffraction Features from (101¯4) Calcite Twins Mimicking Crystallographic Ordering

Recent advances in novel aerogels through the hybrid aggregation of inorganic nanomaterials and polymeric fibers for thermal insulation

Space- and Angle-Resolved Vibrational Spectroscopy to Probe the Local Phonon Modes at Planar Defects

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