Atomic-Resolution STEM at Low Primary Energies

Krivanek, Ondrej L.; Chisholm, Matthew F.; Dellby, Niklas; Murfitt, Matthew F.

doi:10.1007/978-1-4419-7200-2_15

Cited by 11 publications

(5 citation statements)

References 80 publications

(55 reference statements)

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“…For a nonzero probe current, the finite source size also needs to be considered. The size of the electron source projected onto the sample depends on the probe current and the brightness of the electron source as (Krivanek et al, 2011)…”

Section: Resultsmentioning

confidence: 99%

Single Atom Microscopy

et al. 2012

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We show that aberration-corrected scanning transmission electron microscopy operating at low accelerating voltages is able to analyze, simultaneously and with single atom resolution and sensitivity, the local atomic configuration, chemical identities, and optical response at point defect sites in monolayer graphene. Sequential fast-scan annular dark-field (ADF) imaging provides direct visualization of point defect diffusion within the graphene lattice, with all atoms clearly resolved and identified via quantitative image analysis. Summing multiple ADF frames of stationary defects produce images with minimized statistical noise and reduced distortions of atomic positions. Electron energy-loss spectrum imaging of single atoms allows the delocalization of inelastic scattering to be quantified, and full quantum mechanical calculations are able to describe the delocalization effect with good accuracy. These capabilities open new opportunities to probe the defect structure, defect dynamics, and local optical properties in 2D materials with single atom sensitivity.

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Section: Resultsmentioning

confidence: 99%

Single Atom Microscopy

et al. 2012

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“…The ideal OAM beam for STEM applications should have a single, well-defined angular momentum, be similar in size to a single atom, and contain at least about 20 pA of current, so that inner shell loss electron energy-loss spectra (EELS) with acceptable signal-to-noise ratio can be acquired in seconds to minutes. CFE sources can provide coherent currents I c of 400 pA and more (Dellby et al, 2011;Krivanek et al, 2011Krivanek et al, , 2013a and an energy spread of < 0.4 eV. They give a higher current in a given size probe than any other electron source presently available, and should be able to prevent the excessive source size contribution to 1-2 Å vortex beams observed by Verbeeck et al (2011).…”

Section: Methodsmentioning

confidence: 99%

Toward Single Mode, Atomic Size Electron Vortex Beams

et al. 2014

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We propose a practical method of producing a single mode electron vortex beam suitable for use in a scanning transmission electron microscope (STEM). The method involves using a holographic "fork" aperture to produce a row of beams of different orbital angular momenta, as is now well established, magnifying the row so that neighboring beams are separated by about 1 µm, selecting the desired beam with a narrow slit, and demagnifying the selected beam down to 1-2 Å in size. We show that the method can be implemented by adding two condenser lenses plus a selection slit to a straight-column cold-field emission STEM. It can also be carried out in an existing instrument, the monochromated Nion high-energy-resolution monochromated electron energy-loss spectroscopy-STEM, by using its monochromator in a novel way. We estimate that atom-sized vortex beams with ≥ 20 pA of current should be attainable at 100-200 keV in either instrument.

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“…Once spherical aberration has been corrected, the attainable diameter of the STEM's electron beam (typically called the ‘electron probe’) is determined by other parameters: the chromatic aberration C c , the energy spread of the primary beam ∆E, higher‐order (fourth, fifth and above) aberrations, the brightness of the electron source, the current admitted into the electron probe and the precision of the tuning of the aberrations (see Krivanek et al . () for full details). By paying close attention to these secondary factors, the probe size can be improved to about 20 λ.…”

Section: The Quest For Spatial Resolutionmentioning

confidence: 99%

Aberration‐corrected STEM for atomic‐resolution imaging and analysis

Krivanek

Lovejoy

Dellby

2015

Journal of Microscopy

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Aberration-corrected scanning transmission electron microscopes are able to form electron beams smaller than 100 pm, which is about half the size of an average atom. Probing materials with such beams leads to atomic-resolution images, electron energy loss and energy-dispersive X-ray spectra obtained from single atomic columns and even single atoms, and atomic-resolution elemental maps. We review briefly how such electron beams came about, and show examples of applications. We also summarize recent developments that are propelling aberration-corrected scanning transmission electron microscopes in new directions, such as complete control of geometric aberration up to fifth order, and ultra-high-energy resolution EELS that is allowing vibrational spectroscopy to be carried out in the electron microscope.

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Atomic-Resolution STEM at Low Primary Energies

Cited by 11 publications

References 80 publications

Single Atom Microscopy

Single Atom Microscopy

Toward Single Mode, Atomic Size Electron Vortex Beams

Aberration‐corrected STEM for atomic‐resolution imaging and analysis

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