Interferometric 4D-STEM for Lattice Distortion and Stacking Sequence Measurements of Few-layer Two-dimensional Materials.

Van der Waals materials composed of stacks of individual atomic layers have attracted considerable attention due to their exotic electronic properties that can be altered by, for example, manipulating the twist angle of bilayer materials or the stacking sequence of trilayer materials. To fully understand and control the unique properties of these few-layer materials, a technique that can provide information about both local structural deformations and the stacking sequence of these materials is needed. Here, we demonstrate an interferometric four-dimensional scanning transmission electron microscopy technique that allows the relative positions of atoms in separate layers of few-layer materials to be measured with nm-scale resolution. Not only does this enable local measurement of pm-scale in-plane lattice distortions, but it also provides information about the stacking sequence in certain cases, providing a means to better understand the interplay between the electronic properties and precise structural arrangement of few-layer 2D materials.