![]() In all three cases, the STEM/PNBD results were comparable to those obtained from TEM/SAED. We called our new method 4D-STEM/PNBD (Powder NanoBeam Diffraction) and applied it to three different systems: Au nano-islands (well diffracting nanocrystals with size ~20 nm), small TbF 3 nanocrystals (size 100 nm). The final powder diffraction pattern can be analyzed by means of standard programs for TEM/SAED (Selected-Area Electron Diffraction). In our method, all individual diffractograms (showing randomly oriented diffraction spots from a few nanocrystals) are combined into one composite diffraction pattern (showing diffraction rings typical of polycrystalline/powder materials). Nevertheless, the individual 4D-STEM diffractograms are difficult to analyze due to the random orientation of nanocrystalline material. They can be used routinely to collect a high number of electron diffraction patterns from individual nanocrystals and/or locations (this is called four-dimensional scanning transmission electron microscopy (4D-STEM), as we obtain two-dimensional (2D) information for each pixel of the 2D scanning array). The pixelated detectors for SEM have been commercialized recently. The only requirement is that the SEM microscope must be equipped with a pixelated detector of transmitted electrons. We introduce a novel scanning electron microscopy (SEM) method which yields powder electron diffraction patterns. ![]()
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