Transmission electron microscopy at 20kV for imaging and spectroscopy

Kaiser, Ute; Biskupek, Johannes; Meyer, Jannik C.; Leschner, Jens; Lechner, Lorenz; Rose, H.; Stöger-Pollach, Michael; Khlobystov, Andrei N.; Hartel, Peter; Müller, Heiko; Haider, Max; Eyhusen, Soeren; Benner, G.

doi:10.1016/j.ultramic.2011.03.012

Cited by 193 publications

(155 citation statements)

References 29 publications

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“…Modern transmission electron microscopes (TEM) allow imaging materials at a single atom resolution with acceleration voltages in the range of 20-300 kV [1][2][3] , foremost thanks to the practical realization of aberration correctors (AC) for transmission electron microscopy 4,5 . However, high electron doses are required for achieving a high enough signal to noise ratio for accurate detection of the atom position in the image.…”

Section: Introductionmentioning

confidence: 99%

Electron radiation damage mechanisms in 2D MoSe2

Lehnert¹,

Lehtinen²,

Algara‐Siller³

et al. 2017

Applied Physics Letters

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The contributions of different damage mechanisms in single-layer MoSe 2 were studied by investigating different MoSe 2 /graphene heterostructures by aberration-corrected high-resolution transmission electron microscopy (AC-HRTEM) at 80 keV. The damage cross-sections were determined by direct counting of atoms in the AC-HRTEM images. The contributions of damage mechanisms such as knock-on damage or ionization effects were estimated by comparing the damage rates in different heterostructure configurations, similarly to what has been earlier done with MoS 2 . The behaviour of MoSe 2 was found to be nearly identical to that of MoS 2 , which is an unexpected result, as the knock-on mechanism should be suppressed in MoSe 2 due to the high mass of Se as compared to S.

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Section: Introductionmentioning

confidence: 99%

Electron radiation damage mechanisms in 2D MoSe2

Lehnert¹,

Lehtinen²,

Algara‐Siller³

et al. 2017

Applied Physics Letters

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“…11 So far, predominantly low-dimensional materials such as graphene, 5,8,10 hexagonal boron nitride, 6 and carbon nanotubes 7 have been studied at low electron beam voltages by HRTEM. In the future, however, there will be a demand to extend these low-voltage studies to conventional materials, which similarly suffer from knock-on damage at higher voltages.…”

confidence: 99%

Atomic-scale effects behind structural instabilities in Si lamellae during ion beam thinning

et al. 2012

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The rise of nanotechnology has created an ever-increasing need to probe structures on the atomic scale, to which transmission electron microscopy has largely been the answer. Currently, the only way to efficiently thin arbitrary bulk samples into thin lamellae in preparation for this technique is to use a focused ion beam (FIB). Unfortunately, the established FIB thinning method is limited to producing samples of thickness above ∼20 nm. Using atomistic simulations alongside experiments, we show that this is due to effects from finite ion beam sharpness at low milling energies combined with atomic-scale effects at high energies which lead to shrinkage of the lamella. Specifically, we show that attaining thickness below 26 nm using a milling energy of 30 keV is fundamentally prevented by atomistic effects at the top edge of the lamella. Our results also explain the success of a recently proposed alternative FIB thinning method, which is free of the limitations of the conventional approach due to the absence of these physical processes

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Performance of the SALVE-microscope: Atomic-resolution TEM Imaging at 20 kV

et al. 2016

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The SALVE project had been initiated to develop a dedicated low-voltage TEM that is corrected for both, spherical and chromatic aberration, in order to allow atomic resolution TEM observations on beam sensitive materials [1,2].The centerpiece of the SALVE III microscope is CEOS' new Cc-Cs-corrector that is based on the socalled Rose-Kuhn-Design [3,4]. The corrector is incorporated into a cubed FEI Titan Themis TEM and has been aligned for five accelerating voltages in the range from 20 to 80kV. During corrector design special care had to be taken to avoid the resolution limiting effects of thermal magnetic field noise (Johnson-Nyquist noise) that effectively limits the information transfer in Cc-corrected electron microscopes [5]. As seen in Table 1, these measures have been successful in that for all desired high-tensions the resulting final resolutions exceed the desired 50mrad aperture. Figure 1(a) exemplarily demonstrates the achieved information limit at an accelerating voltage of 20kV. For the two perpendicular directions the Young's fringes on a purely amorphous 2nm tungsten sample significantly exceed the 50mrad radius. In order to "use" the transferred information adequately, the phase plate, i.e. the aberration function, has to be well-controlled beyond the 50mrad-angle. This requires access up to including 5th order axial aberrations, and -for a considerable field of view-control over off-axial aberrations. The aberration measurement in Figure 1(b) demonstrates that all unround axial aberrations as well as the off-axial aberrations can be tuned sufficiently small. At the same time, the round aberrations can be adjusted for a suitable phase contrast transfer function (indicated in green color). Consequently, as visible in Figure 1(c) atomic resolution imaging at 20kV becomes reality. Chromatic aberration causes inelastically scattered electrons, i.e. electrons of lower energy, to be focused much stronger. This is not true in the Cc-corrected instrument. Figure 1(d) compares the energydependent defocus effect at 20kV of a Cc-uncorrected TEM (red line, Cc=1.45mm) and the SALVE microscope (measurements: black dots, 3rd order fit: dashed line). The magnified area indicates that EFTEM with significant energy windows is possible even at 20kV enabling new modes of operation such as high-resolution EFTEM at very low voltages. [6] References:[1] U. Kaiser et al.,

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Transmission electron microscopy at 20kV for imaging and spectroscopy

Cited by 193 publications

References 29 publications

Electron radiation damage mechanisms in 2D MoSe2

Electron radiation damage mechanisms in 2D MoSe2

Atomic-scale effects behind structural instabilities in Si lamellae during ion beam thinning

Performance of the SALVE-microscope: Atomic-resolution TEM Imaging at 20 kV

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