Fast Pixelated Detectors in Scanning Transmission Electron Microscopy. Part II: Post-Acquisition Data Processing, Visualization, and Structural Characterization

Abstract

Abstract

A Comparison of a Direct Electron Detector and a High-Speed Video Camera for a Scanning Precession Electron Diffraction Phase and Orientation Mapping

“…Such techniques are known to work well even with noisy data, so it is highly likely that the improved data quality from the direct electron detector will allow the successful application of such methods at very low electron doses of a few e − /Å 2 , just as was recently performed using scanned electron nanodiffraction for a beam-sensitive halide perovskite (Doherty et al, 2020). Further data analysis could be performed in some cases using different approaches, by integrating the intensity of specific parts of a diffraction pattern (possibly with background subtraction), as has been done in other analyses of pixelated detector data from STEM (Nord et al, 2019a(Nord et al, , 2019bPaterson et al, 2020). This could be done, for example, to study the ordering or domain variant selection in materials, by the appearance and orientation of superlattice spots.…”

Fast Pixelated Detectors in Scanning Transmission Electron Microscopy. Part I: Data Acquisition, Live Processing, and Storage

“…One such example is the work by NanoMEGAS to incorporate a Medipix3 DED into their DigiSTAR precession system in order to enable high fidelity recording of diffraction patterns in scanning PED (SPED) applications, as has been demostrated in recent work (MacLaren et al, 2020). Additional benefits brought about by the use of DEDs in SPED will be discussed in Part II of this work (Paterson et al, 2020b). We note here, however, that the properties of the 4D dataset obtained by such a system are in many ways equivalent to those of 4D non-SPED datasets, and so many of the same issues of data access, storage, and processing apply here too.…”

“…processing are covered in Part II of this work (Paterson et al, 2020b), while field mapping will be covered in Part III.…”

“…However, a very simple method that often allows for similar read speed while maintaining flexibility is to read images (when they are needed as full images) from a hypercube chunked dataset in numbers that are aligned to a chunk size. This is the approach of data processing using the fpd package, which is discussed in more detail in Part II (Paterson et al, 2020b). For the example in Figure 6f, taking length 16 hypercubes as the reference, reading 16 × 16 images with hyperrectangles of length 1 takes 0.95× the reference time, while reading the same with hyperrectangles of length 16 takes 1.12× the reference time.…”

“…The post-acquisition visualization and processing of data from fast pixelated detectors using the fpd and pixStem 1 libraries for the structural characterization of materials will be reported in Part II of this work (Paterson et al, 2020b). A third and final part (yet to be submitted) will cover aspects related to differential phase contrast analysis.…”