Contrast reversal in atomic-scale phonon spectroscopic imaging

Hage, F.; Ramasse, Quentin M.; Allen, L. J.

doi:10.1103/physrevb.102.214111

Cited by 12 publications

(9 citation statements)

References 29 publications

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“…The magnon signal of the BF detector shows expected strong dynamical diffraction effects with volcano-shaped features around the atomic columns. A similar behavior was reported in phonon EELS maps [30]. The contrast is lower with a ratio of maximal to minimal intensities near a factor of 5, while the relative strength of the magnon signal remains below 10 −6 , at a similar level to the magnon signal collected by the HAADF detector.…”

supporting

confidence: 80%

Magnon diffuse scattering in scanning transmission electron microscopy

Lyon,

Bergman,

Zeiger

et al. 2021

Preprint

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We present a theory and a simulation of thermal diffuse scattering due to the excitation of magnons in scanning transmission electron microscopy. The calculations indicate that magnons can present atomic contrast when detected by electron energy-loss spectroscopy using atomic-size electron beams. The results presented here indicate that the intensity of the magnon diffuse scattering in bcc iron at 300 K is 4 orders of magnitude weaker than the intensity of thermal diffuse scattering arising from atomic vibrations. In an energy range where the phonon and magnon dispersions do not overlap, a monochromated scanning transmission electron microscope equipped with direct electron detectors for spectroscopy is expected to resolve the magnon spectral signatures.

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supporting

confidence: 80%

Magnon diffuse scattering in scanning transmission electron microscopy

Lyon,

Bergman,

Zeiger

et al. 2021

Preprint

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“…So far, two-dimensional (2D) mapping of surface and bulk excitations 23 and detection of single-atom 24 and defect 25 vibrational signals have been achieved. Although dipole scattering in polar materials, such as BN 21 , 26 , 27 , MgO 23 and SiC 20 , 28 , under on-axis scanning transmission electron microscopy-electron energy loss spectroscopy (STEM-EELS) the geometry produces long-range and non-local polariton modes, reducing the atomic-scale contrast in vibrational EELS signal mapping 29 , dipole scattered signals are substantially suppressed and negligible in elemental and non-polar materials with weak dipoles, such as Si 22 and SiGe, which only contain highly localized phonon scattering. Here, we report quantitative high spatial resolution mapping of phonons in SiGe QDs using an on-axis beam-detector geometry (Extended Data Fig.…”

Section: Mainmentioning

confidence: 99%

“…The variation of vibrational signal in the line scan (Extended Data Fig. 8b ) presumably arises from the short-range coulomb interaction between the beam and the atomic nucleus, providing atomic-scale contrast 29 . Interestingly, even when the maximum peak heights are normalized to 1, the Ge OM still shows a strong modulation.…”

Section: Mainmentioning

confidence: 99%

Nanoscale imaging of phonon dynamics by electron microscopy

Gadre

Yan

Song

et al. 2022

Nature

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Spatially resolved vibrational mapping of nanostructures is indispensable to the development and understanding of thermal nanodevices1, modulation of thermal transport2 and novel nanostructured thermoelectric materials3–5. Through the engineering of complex structures, such as alloys, nanostructures and superlattice interfaces, one can significantly alter the propagation of phonons and suppress material thermal conductivity while maintaining electrical conductivity2. There have been no correlative experiments that spatially track the modulation of phonon properties in and around nanostructures due to spatial resolution limitations of conventional optical phonon detection techniques. Here we demonstrate two-dimensional spatial mapping of phonons in a single silicon–germanium (SiGe) quantum dot (QD) using monochromated electron energy loss spectroscopy in the transmission electron microscope. Tracking the variation of the Si optical mode in and around the QD, we observe the nanoscale modification of the composition-induced red shift. We observe non-equilibrium phonons that only exist near the interface and, furthermore, develop a novel technique to differentially map phonon momenta, providing direct evidence that the interplay between diffuse and specular reflection largely depends on the detailed atomistic structure: a major advancement in the field. Our work unveils the non-equilibrium phonon dynamics at nanoscale interfaces and can be used to study actual nanodevices and aid in the understanding of heat dissipation near nanoscale hotspots, which is crucial for future high-performance nanoelectronics.

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“…The possibility of atomic-resolution phonon mapping was proposed (Lugg et al, 2015 a ; Dwyer, 2017; Hage et al, 2019) and practically realized by Venkatraman et al (2019) (Fig. 8), although the fundamental localization mechanisms and image contrast still need to be carefully evaluated (Hage et al, 2020 b ; Rez & Singh, 2021). Hage et al (2020 a ) demonstrated the detection of distinctive localized vibrational signatures from a single-atom impurity in a solid (Si atom in graphene), clearly demonstrating single-atom sensitivity by STEM vibrational spectroscopy and inviting intriguing implications across the fields of physics, chemistry, and materials science.…”

Section: Development Of the Scanning Transmission Electron Microscopementioning

confidence: 99%

Advances and Applications of Atomic-Resolution Scanning Transmission Electron Microscopy

Liu

2021

Microsc Microanal

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Although scanning transmission electron microscopy (STEM) images of individual heavy atoms were reported 50 years ago, the applications of atomic-resolution STEM imaging became wide spread only after the practical realization of aberration correctors on field-emission STEM/TEM instruments to form sub-Ångstrom electron probes. The innovative designs and advances of electron optical systems, the fundamental understanding of electron–specimen interaction processes, and the advances in detector technology all played a major role in achieving the goal of atomic-resolution STEM imaging of practical materials. It is clear that tremendous advances in computer technology and electronics, image acquisition and processing algorithms, image simulations, and precision machining synergistically made atomic-resolution STEM imaging routinely accessible. It is anticipated that further hardware/software development is needed to achieve three-dimensional atomic-resolution STEM imaging with single-atom chemical sensitivity, even for electron-beam-sensitive materials. Artificial intelligence, machine learning, and big-data science are expected to significantly enhance the impact of STEM and associated techniques on many research fields such as materials science and engineering, quantum and nanoscale science, physics and chemistry, and biology and medicine. This review focuses on advances of STEM imaging from the invention of the field-emission electron gun to the realization of aberration-corrected and monochromated atomic-resolution STEM and its broad applications.

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Contrast reversal in atomic-scale phonon spectroscopic imaging

Abstract: This is a repository copy of Contrast reversal in atomic-scale phonon spectroscopic imaging.

Cited by 12 publications

References 29 publications

Magnon diffuse scattering in scanning transmission electron microscopy

Magnon diffuse scattering in scanning transmission electron microscopy

Nanoscale imaging of phonon dynamics by electron microscopy

Advances and Applications of Atomic-Resolution Scanning Transmission Electron Microscopy

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