Phase reconstruction using fast binary 4D STEM data

We report the application of focused probe ptychography using binary 4D datasets obtained using scanning transmission electron microscopy (STEM). Modern fast pixelated detectors have enabled imaging of individual convergent beam electron diffraction patterns in a STEM raster scan at frame rates in the range of 1000-8000 Hz using conventional counting modes. Changing the bit depth of a counting detector, such that only values of 0 or 1 can be recorded at each pixel, allows one to decrease the dwell time and increase the frame rate to 12.5 kHz, reducing the electron exposure of the sample for a given beam current. Atomically resolved phase contrast of an aluminosilicate zeolite (ZSM-5) is observed from sparse diffraction patterns with isolated individual electrons, demonstrating the potential of binary ptychography as a low-dose 4D STEM technique.