Effects of instrument imperfections on quantitative scanning transmission electron microscopy

Krause, Florian; Schowalter, Marco; Grieb, Tim; Müller‐Caspary, Knut; Mehrtens, Thorsten; Rosenauer, Andreas

doi:10.1016/j.ultramic.2015.10.026

Cited by 58 publications

(48 citation statements)

References 29 publications

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“…The intensity I 0 of the incoming STEM beam was measured from conventional “detector scans”22956 (Supplementary Fig. S1: detector scans for the GaNAs study), which are acquired by scanning the primary beam over the high-angle annular dark field detector (Fischione 3000) in imaging mode without specimen.…”

Section: Methodsmentioning

confidence: 99%

“…First, azimuthal averages are calculated from the detector scans just mentioned, being the conventional method to obtain the radial sensitivity2. Second, the incident STEM beam is tilted systematically while the microscope is set to diffraction mode so as to cover the angular domain transferred by the imaging system56. Such tilt-based detector scans fully include all distortions of the diffraction pattern caused by the aberration corrector for imaging.…”

Section: Methodsmentioning

confidence: 99%

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Materials characterisation by angle-resolved scanning transmission electron microscopy

Müller‐Caspary

Oppermann

Grieb

et al. 2016

Sci Rep

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Solid-state properties such as strain or chemical composition often leave characteristic fingerprints in the angular dependence of electron scattering. Scanning transmission electron microscopy (STEM) is dedicated to probe scattered intensity with atomic resolution, but it drastically lacks angular resolution. Here we report both a setup to exploit the explicit angular dependence of scattered intensity and applications of angle-resolved STEM to semiconductor nanostructures. Our method is applied to measure nitrogen content and specimen thickness in a GaNxAs1−x layer independently at atomic resolution by evaluating two dedicated angular intervals. We demonstrate contrast formation due to strain and composition in a Si- based metal-oxide semiconductor field effect transistor (MOSFET) with GexSi1−x stressors as a function of the angles used for imaging. To shed light on the validity of current theoretical approaches this data is compared with theory, namely the Rutherford approach and contemporary multislice simulations. Inconsistency is found for the Rutherford model in the whole angular range of 16–255 mrad. Contrary, the multislice simulations are applicable for angles larger than 35 mrad whereas a significant mismatch is observed at lower angles. This limitation of established simulations is discussed particularly on the basis of inelastic scattering.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Materials characterisation by angle-resolved scanning transmission electron microscopy

Müller‐Caspary

Oppermann

Grieb

et al. 2016

Sci Rep

Self Cite

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“…Scanning with dwell-times faster than this decay introduces issues such as increased background and loss of contrast, streaking in real-space and a diffuse noise band in Fourier-space [5]. In spite of these problems, previous literature has shown that PMT based detectors are in fact sensitive to even single electron signals [3,4,6], unfortunately they are also highly inhomogeneous in their collection efficiency [7].One solution to this is to as whether we can form an image using these signals using a pulse read-out? Such an image would record the arriving electron as a single impact-event rather than a streak (perfect MTF), the results would be digital rather than analogue, and all electrons would be recorded with equal sensitivity (perfect DQE).…”

mentioning

confidence: 99%

mentioning

confidence: 99%

The MTF & DQE of Annular Dark Field STEM: Implications for Low-dose Imaging and Compressed Sensing

Jones

Downing

2018

Microsc Microanal

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Annular dark-field imaging in the scanning transmission electron microscope (ADF-STEM) is a hugely useful incoherent imaging mode, yielding monotonically increasing mass / thickness contrast facilitating quantitative compositional mapping, atom-counting, structure-solving and even unstained biologicalimaging [1]. With increasing interest in beam-sensitive materials, many people would like to perform ultra-low-dose imaging or compressed-sensing (CS). Unfortunately, some CS implementations require complex blankers/mask/shutters and may require expensive instrument modification; fast-scanning on the other hand should in principle be available to everyone.Nearly all installed ADF detectors follow the same basic design comprising; a scintillator, light-pipe, PMT, amplifier and a digitiser outputting in arbitrary uncalibrated units [2]. While the scintillator material itself may have an afterglow of only some tens of nanoseconds, the combined assembly has a decay constant of the order of 1.7-3µs which becomes significant in some cases [3,4]. Scanning with dwell-times faster than this decay introduces issues such as increased background and loss of contrast, streaking in real-space and a diffuse noise band in Fourier-space [5]. In spite of these problems, previous literature has shown that PMT based detectors are in fact sensitive to even single electron signals [3,4,6], unfortunately they are also highly inhomogeneous in their collection efficiency [7].One solution to this is to as whether we can form an image using these signals using a pulse read-out? Such an image would record the arriving electron as a single impact-event rather than a streak (perfect MTF), the results would be digital rather than analogue, and all electrons would be recorded with equal sensitivity (perfect DQE). The integer nature of the resulting image signal would also directly benefit quantitative contrast (fractional-beam) studies, statistical image analysis, and compressed-sensing / image-inpainting.In this presentation, we will present a new tool to generate realistic noise realisations from ADF imagesimulations. This tool registers each electron of a finite dose passing through the sample, to the detector (incorporating afterglow), and onward to amplifiers with realistic thermal and electronic noise ( Figure 1). This tool is verified against previous experimental observations of the behaviour of fast-scanned images [5], and is used to explore the modulation transfer function (MTF) of ADF-STEM for various dwell-times (Figure 2).We then propose, and demonstrate using both simulations and experiment (Figure 3), a new method for operating an ADF detector in a pulse read-out mode (which we call ADFpro) using dwell-times of 0.5µs and 0.2µs. The detector's quantum efficiency is evaluated indirectly through the evaluation of image pixel-value histograms but also directly using ADF-detector sensitivity maps. The limitations of this approach will be presented, as well as the implications for ultra-low-dose imaging and for compressedsensing / image-...

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“…Experimental work over this period focused on reducing the electron dose required for imaging radiation-sensitive samples. This reduction in dose was achieved by spreading the dose out over several copies of the sample (as in cryo electron microscopy) and by increasing the signal-to-noise ratio in noisy images acquired at low doses through image processing and electron counting [18][19][20][21][22][23][24][25][26][27][28][29]. However, this research used conventional microscopic imaging methods and did not exploit the reduction in dose enabled by quantum protocols.…”

Section: Introductionmentioning

confidence: 99%

Reduced damage in electron microscopy by using interaction-free measurement and conditional reillumination

et al. 2019

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Interaction-free measurement (IFM) has been proposed as a means of high-resolution, low-damage imaging of radiation-sensitive samples, such as biomolecules and proteins. The basic setup for IFM is a Mach-Zehnder interferometer, and recent progress in nanofabricated electron diffraction gratings has made it possible to incorporate a Mach-Zehnder interferometer in a transmission-electron microscope (TEM). Therefore, the limits of performance of IFM with such an interferometer and a shot-noise limited electron source (such as that in a TEM) are of interest. In this work, we compared the error probability and sample damage for ideal IFM and classical imaging schemes, through theoretical analysis and numerical simulation. We considered a sample that is either completely transparent or completely opaque at each pixel. In our analysis, we also evaluated the impact of an additional detector for scattered electrons. The additional detector resulted in reduction of error by up to an order of magnitude, for both IFM and classical schemes. We also investigated a sample re-illumination scheme based on updating priors after each round of illumination and found that this scheme further reduced error by a factor of two. Implementation of these methods is likely achievable with existing instrumentation and would result in improved resolution in low-dose electron microscopy.

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Effects of instrument imperfections on quantitative scanning transmission electron microscopy

Cited by 58 publications

References 29 publications

Materials characterisation by angle-resolved scanning transmission electron microscopy

Materials characterisation by angle-resolved scanning transmission electron microscopy

The MTF & DQE of Annular Dark Field STEM: Implications for Low-dose Imaging and Compressed Sensing

Reduced damage in electron microscopy by using interaction-free measurement and conditional reillumination

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