What is 4D-STEM?

4D-STEM (four-dimensional scanning transmission electron microscopy) is an advanced electron microscopy technique. It involves scanning a focused electron probe across a sample and, at each probe position, recording a two-dimensional diffraction pattern. This results in a four-dimensional dataset (2D scan positions + 2D diffraction pattern). It allows for the extraction of a wealth of information about the sample's structure, strain, and electromagnetic fields at high spatial resolution. Common uses include characterizing materials at the nanoscale, mapping local atomic arrangements, and studying phase transformations.