Resolution enhancement in transmission electron microscopy with 60-kV monochromated electron source

Morishita, Shigeyuki; Mukai, Masakazu; Suenaga, Kazu; Sawada, Hidetaka

doi:10.1063/1.4939653

Cited by 33 publications

(24 citation statements)

References 16 publications

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“…In principle, the focal spread that determines the information limit of an HRTEM image is basically limited by chromatic aberration of the objective lens and energy spread of the beam 164,165. To improve the image resolution under low‐kV, two simple strategies are straightforward: i) to decrease the specimen thickness for minimized chromatic aberration effects on the resolution degradation and ii) to minimize the energy spread of electron beam by using a monochromator158,166–169 or cold‐FEG 170…”

Section: Technological and Methodological Innovationsmentioning

confidence: 99%

Imaging Beam‐Sensitive Materials by Electron Microscopy

et al. 2020

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Electron microscopy allows the extraction of multidimensional spatiotemporally correlated structural information of diverse materials down to atomic resolution, which is essential for figuring out their structureproperty relationships. Unfortunately, the high-energy electrons that carry this important information can cause damage by modulating the structures of the materials. This has become a significant problem concerning the recent boost in materials science applications of a wide range of beam-sensitive materials, including metal-organic frameworks, covalent-organic frameworks, organicinorganic hybrid materials, 2D materials, and zeolites. To this end, developing electron microscopy techniques that minimize the electron beam damage for the extraction of intrinsic structural information turns out to be a compelling but challenging need. This article provides a comprehensive review on the revolutionary strategies toward the electron microscopic imaging of beamsensitive materials and associated materials science discoveries, based on the principles of electron-matter interaction and mechanisms of electron beam damage. Finally, perspectives and future trends in this field are put forward. he worked as a postdoctoral fellow and research scientist at King Abdullah University of Science and Technology. His research interests now focus on low-dose electron microscopy and structural elucidation of beam-sensitive materials for applications such as catalysis, gas separation, and energy conversion/storage.

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Section: Technological and Methodological Innovationsmentioning

confidence: 99%

Imaging Beam‐Sensitive Materials by Electron Microscopy

et al. 2020

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“…Excellent spatial resolution is the highlight of the transmission electron microscope [1][2][3][4][5][6], allowing atomically resolved elemental mapping and chemistry. Recent instrumental developments have improved the energy resolution of electron energy loss spectroscopy down to 4.2 meV [7,8].…”

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confidence: 99%

Efficient and Versatile Model for Vibrational STEM-EELS

Zeiger

Rusz

2020

Phys. Rev. Lett.

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We introduce a novel method for the simulation of the impact scattering in vibrational scanning transmission electron microscopy electron energy loss spectroscopy (STEM-EELS) simulations. The phonon-loss process is modeled by a combination of molecular dynamics and elastic multislice calculations within a modified frozen phonon approximation. The key idea is thereby to use a so-called δ-thermostat in the classical molecular dynamics simulation to generate frequency dependent configurations of the vibrating specimen's atomic structure. The method includes correlated motion of atoms and provides vibrational spectrum images at the cost comparable to standard frozen phonon calculations. We demonstrate good agreement of our method with simulations and experiments for a 15 nm flake of hexagonal boron-nitride (hBN).Excellent spatial resolution is the highlight of the transmission electron microscope [1-6], allowing atomically resolved elemental mapping and chemistry. Recent instrumental developments have improved the energy resolution of electron energy loss spectroscopy down to 4.2 meV [7,8]. This unique combination of high spatial and energy resolution opened doors to unprecedented experiments such as temperature measurement at the nanoscale [9, 10], identification and mapping of isotopically labeled molecules [11], position-and momentum-resolved mapping of phonon modes [12,13], mapping of bulk and surface modes of nanocubes [14], or investigations of the nature of polariton modes in van der Waals crystals [15].Inelastic electron scattering on atomic vibrations in a polar material consists of two major contributions, namely, impact scattering and dipolar scattering [16,17]. The latter stems from a long ranged interaction between the beam electron and an oscillating dipole moment generated by the atomic vibrations. It can be used to perform damage-free vibrational spectroscopy in an aloof beam geometry [18,19]. High-angle impact scattering on the other hand is quite localized scattering on the atomic potential and allows for high resolution imaging and spectroscopy [17,[20][21][22].From a theoretical point of view, there is a limited number of approaches one can follow to simulate vibrational spectroscopy and imaging. Dwyer presents a treatment of both single impact and single dipolar scattering including a detailed phonon dispersion from a density functional theory calculation in a multislice scheme [23]. Forbes et al. introduced a quantum excitation of phonons model, which allows for the inclusion of thermal diffuse scattering into multislice image simulations [24]. The thermal vibrations are modeled within the Einstein model for quick image calculations, neglecting correlations in atomic movements and dispersion effects. Such an approach is not able to simulate vibrational spectra but in principle one could use different models of atomic vibrations to generate the necessary configurations. In a more recent work, Forbes et al. described a method to model the vibrational sector of the electron energy loss spectrum [25...

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“…The second key factor to degrade resolution at low accelerating voltages is defocus spread caused by chromatic aberration. The defocus spread Δ caused by chromatic aberration is expressed as Δ = Cc dE/E, where Cc is the chromatic aberration coefficient and dE is the deviation of the electron energy E. Although the defocus spread can be affected by deviations of the accelerating voltage and lens current, they can be neglected at low accelerating voltages [17].…”

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confidence: 99%

Atomic Resolution Imaging at an Ultralow Accelerating Voltage by a Monochromatic Transmission Electron Microscope

et al. 2016

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Transmission electron microscopy using low-energy electrons would be very useful for atomic resolution imaging of specimens that would be damaged at higher energies. However, the resolution at low voltages is degraded because of geometrical and chromatic aberrations. In the present study, we diminish the effect of these aberrations by using a delta-type corrector and a monochromator. The dominant residual aberration in a delta-type corrector, which is the sixth-order three-lobe aberration, is counterbalanced by other threefold aberrations. Defocus spread caused by chromatic aberration is reduced by using a monochromated beam with an energy spread of 0.05 eV. We obtain images of graphene and demonstrate atomic resolution at an ultralow accelerating voltage of 15 kV.

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Resolution enhancement in transmission electron microscopy with 60-kV monochromated electron source

Cited by 33 publications

References 16 publications

Imaging Beam‐Sensitive Materials by Electron Microscopy

Imaging Beam‐Sensitive Materials by Electron Microscopy

Efficient and Versatile Model for Vibrational STEM-EELS

Atomic Resolution Imaging at an Ultralow Accelerating Voltage by a Monochromatic Transmission Electron Microscope

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