Abstract text (incl. figure legends and references)
SavvyScan is a system that incorporates flexible pattern scanning and simultaneous acquisition from multiple diffraction detector segments in a Scanning Transmission Electron Microscope (STEM). The microscope operations are fully manageable by SerialEM while the extended hardware is based on multipurpose PC cards from Spectrum Instrumentation GmbH. Interface software is released as open source. In the first publication of the system we presented spiral scans of integrated differential phase contrast (iDPC) images and introduced the useful idea of splitting iDPC to separate depth contrast and phase contrast based on image shift corrections (1). Here we report on recent enhancements to the system. The range of image sizes has been extended based on first-in-first-out acquisition that is in principle limitless. The rate of digital averaging has been extended to maximum to improve signal to noise ratio and the channels are processed and recorded simultaneously to shorten acquisition time. The system now supports automated tilt series acquisition at multiple sites based on the navigation features in SerialEM. SavvyScan software recognizes the Record scans and save them in a multi-slice mrc format per detector channel. The newly supported remote Python scripting in SerialEM is utilized for special tasks such as automated alignment of the diffraction disk at high precision. Additional scan patterns have been introduced, including Lissajous curve and continuous 4X4 raster scans that may potentially reduce instability artifacts in single particle analysis. We learn to exploit the multiple signals from concentric annular segments on the Opal diode (El-Mul Technologies) and HAADF (Fischione) detectors for discrimination of materials on the basis of atomic stoichiometry.
(1) Seifer, S.; Houben, L.; Elbaum, M. Flexible STEM with Simultaneous Phase and Depth Contrast. Microscopy and Microanalysis 2021, 1–12. https://doi.org/10.1017/S1431927621012861.