Developments in EELS instrumentation for spectroscopy and imaging

Krivanek, Ondrej L.; Gubbens, A.J.; Dellby, Niklas

doi:10.1051/mmm:0199100202-3031500

Cited by 127 publications

(34 citation statements)

References 12 publications

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“…Spectra produced at the energy-selecting slit or at the SSC are free of ail first and secondorder aberrations, and images formed by the imaging assembly are also free of all important first and second-order aberrations and distortions [14]. Because the filter focuses on the final TEM crossover which occurs just below the last projector lens under all normal TEM imaging and diffraction conditions, operation of the filter and of the TEM are largely independent.…”

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confidence: 97%

“…A detailed description of the electron-optical design of our filter has been given elsewhere [14]. Here we briefly review its electron optics and principal components, describe the principles governing the design of its electronics and computer software, and give several examples demonstrating the performance of the filter on practical applications.…”

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confidence: 99%

“…The first-order aberrations and distortions can be removed by placing several round lenses plus quadrupole lenses [11], or quadrupoles alone [12] [13,14]. Image quality is then limited only by thirdorder aberrations and distortions, and recorded images of 1024 x 1024 pixels are indistinguishable from images recorded by even the most highly corrected 03A9-filters, which employ 4 magnetic sectors and 7 sextupoles [7].…”

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confidence: 99%

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Design and first applications of a post-column imaging filter

Krivanek¹,

Gubbens²,

Dellby³

et al. 1992

Microsc. Microanal. Microstruct.

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144

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Abstract. 2014 We have designed and built an imaging filter which can be attached to most standard TEMs, and is capable of operating at primary energies of up to 400 keV. The filter uses a 90°m agnetic sector prism, a piezoelectrically controlled energy-selecting slit, and 6 quadrupole and 5 sextupole lenses. It fully corrects second-order aberrations and distortions in images formed with electrons of selected energies, and it also produces second-order aberration-corrected spectra of variable dispersion. We show the first applications of the filter at 200 keV primary energy, which indicate that the filter will excel in chemical mapping and spectroscopy, in improving contrast of electron images and diffraction patterns, and in making high resolution electron microscopy and diffraction more quantitative. We conclude the paper with a discussion about atomic resolution image formation using inelastically scattered electrons, and the relationship between energy-filtered diffraction patterns and images formed with electrons of the same energy.

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Design and first applications of a post-column imaging filter

Krivanek¹,

Gubbens²,

Dellby³

et al. 1992

Microsc. Microanal. Microstruct.

Self Cite

144

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“…Both, the in-column filter by Carl Zeiss [1] and the Gatan Imaging Filter [2] have proven useful and are well documented. Compared to TEM, energy filtering combined with BF-STEM has seen less publicity.…”

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confidence: 99%

Energy Filtered STEM Imaging at 30kV and Below - A New Window into the Nano-World?

et al. 2017

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Energy filtered imaging has been available for many years for TEMs. Both, the in-column filter by Carl Zeiss [1] and the Gatan Imaging Filter [2] have proven useful and are well documented. Compared to TEM, energy filtering combined with BF-STEM has seen less publicity. This is surprising because BF-STEM by itself has an advantage over TEM: inelastically scattered electrons have less of an effect on the final image quality when compared to TEM. Furthermore, EF (energy-filtered) BF-STEM imaging has been reported as a promising approach [3]. However, EF BF-STEM imaging is handicapped by the requirement of a fast EELS detector: for acquiring a 512 × 512 pixel image in under 1s, an EELS detector capable of 512 × 512 = 262,144 EELS spectra /s is required.For this study, the recently announced Hitachi's Low-Voltage STEM/SEM with EELS [4] presents an opportunity for further investigating the differences between TEM and BF-STEM imaging. Its cold FEG (field emission gun) and immersion lens allow for high resolution imaging. It also has two EELS detectors integrated into one system: one for acquiring a typical EELS spectrum, the other using a threeelement detector capable of reading the ZLP and two Plasmon peaks in excess of 11,000 times/s. As a result, image acquisition is possible at ~0.2fps for a 256 × 256 image. Thus samples can be investigated with (EF) BF-STEM and Plasmon imaging at relatively low energies at, or close to, atomic resolution. But compared to TEM, 30keV seems a rather low voltage for imaging, but it is not as will be shown.In its simplest form, energy filtering improves image quality by removing inelastic scattered electrons. In a very recent study [5], C C corrected images were compared with non-corrected images. As expected, compensating the optical artifacts from inelastically scattered electrons improved the image quality throughout. The benefit of a C C corrected systems is that the majority of the inelastically scatter electrons remain with the final image and thus the increase in the stochastic noise (due to finite number of electrons) is small. In contrast, non-C C corrected systems remove inelastically scattered electrons and thus can increase the stochastic noise in the final image significantly. Thus, removal of the inelastically scattered electrons causes a loss of electrons (bad) but also causes less artifacts (good) for (EF) BF-STEM. Therefore we ask: how would a 30keV (EF) BF-STEM compare to a higher-kV TEM?We are presenting here our first results comparing 30keV BF-STEM, EF BF-STEM and Plasmon images with TEM images at 80keV and 120keV. The comparison is presented in Figure 1 where, to the left, the standard 30keV BF-STEM image is shown; on the right the 30keV EF BF-STEM image and Plasmon image appears; and in the middle of Figure 1, the corresponding TEM images are shown with the 120keV TEM image above the 80keV TEM image. These initial results indicate that 30keV (EF) BF-STEM images compare less with 120keV TEM images but compare well with 80keV TEM images.Why is this important? The ...

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“…EELS sensitivity has been greatly increased by using multi-channel arrays to detect in parallel the inelastically scattered electrons [3]. This [4] or as a post-column imaging filter behind [5] are commercially available and they are shown in figure 1. Similarly to X-ray mapping using a Scanning Transmission Electron Microscope (STEM) coupled with an Energy Dispersive X-ray Spectrometer (EDXS), some laboratories are performing elemental mapping using STEM coupled with PEELS. The use of a PEELS coupled with a STEM was first introduced by Jeanguillaume and Colliex [7] as the "Spectrum-Imaging" method.…”

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confidence: 99%