interactive 4D-STEM
Watch the diffraction pattern change as you scan an electron probe across a polycrystalline sample.
Move the scan-position slider to sweep the electron probe across the polycrystalline sample and see how the diffraction pattern changes as it crosses each grain. The convergence semiangle switches between nanobeam diffraction (small semiangle, separated Bragg disks) and ptychographic imaging conditions (large semiangle, overlapping disks).
What is 4D-STEM?
In scanning transmission electron microscopy (STEM), a focused electron probe is rastered across the sample. In 4D-STEM, a fast pixelated detector records a full 2D diffraction pattern at every 2D probe position, giving a four-dimensional dataset. That one dataset can be analyzed after the experiment in many ways: virtual imaging, crystal orientation and strain mapping, or phase retrieval with ptychography.
Open-source tools for this analysis include quantEM and py4DSTEM.