60 research outputs found
Interlacing in atomic resolution scanning transmission electron microscopy
Fast frame-rates are desirable in scanning transmission electron microscopy
for a number of reasons: controlling electron beam dose, capturing in-situ
events or reducing the appearance of scan distortions. Whilst several
strategies exist for increasing frame-rates, many impact image quality or
require investment in advanced scan hardware. Here we present an interlaced
imaging approach to achieve minimal loss of image quality with faster
frame-rates that can be implemented on many existing scan controllers. We
further demonstrate that our interlacing approach provides the best possible
strain precision for a given electron dose compared with other contemporary
approaches
Increasing Spatial Fidelity and SNR of 4D-STEM using Multi-frame Data Fusion
4D-STEM, in which the 2D diffraction plane is captured for each 2D scan
position in the scanning transmission electron microscope (STEM) using a
pixelated detector, is complementing and increasingly replacing existing
imaging approaches. However, at present the speed of those detectors, although
having drastically improved in the recent years, is still 100 to 1,000 times
slower than the current PMT technology operators are used to. Regrettably, this
means environmental scanning-distortion often limits the overall performance of
the recorded 4D data. Here we present an extension of existing STEM distortion
correction techniques for the treatment of 4D-data series. Although applicable
to 4D-data in general, we use electron ptychography and electric-field mapping
as model cases and demonstrate an improvement in spatial-fidelity,
signal-to-noise ratio (SNR), phase-precision and spatial-resolution
How Fast is Your Detector? The Effect of Temporal Response on Image Quality
With increasing interest in high-speed imaging should come an increased
interest in the response times of our scanning transmission electron microscope
(STEM) detectors. Previous works have previously highlighted and contrasted
performance of various detectors for quantitative compositional or structural
studies, but here we shift the focus to detector temporal response, and the
effect this has on captured images. The rise and decay times of eight
detectors' single electron response are reported, as well as measurements of
their flatness, roundness, smoothness, and ellipticity. We develop and apply a
methodology for incorporating the temporal detector response into simulations,
showing that a loss of resolution is apparent in both the images and their
Fourier transforms. We conclude that the solid-state detector outperforms the
photomultiplier-tube (PMT) based detectors in all areas bar a slightly less
elliptical central hole and is likely the best detector to use for the majority
of applications. However, using tools introduced here we encourage users to
effectively evaluate what detector is most suitable for their experimental
needs
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