Interferometric 4D-STEM for Lattice Distortion and Interlayer Spacing Measurements in Bilayer and Trilayer Two-dimensional Materials

TL;DR

This paper introduces an interferometric 4D-STEM technique that captures detailed 3D structural information of bilayer and trilayer 2D materials, enabling precise measurements of lattice distortions, twist angles, and interlayer spacings at nanometer resolution.

Contribution

The paper presents a novel interferometric 4D-STEM method for detailed structural analysis of few-layer 2D materials, providing insights into their local lattice distortions and interlayer arrangements.

Findings

Achieved pm-scale accuracy in measuring lattice distortions.

Successfully determined twist directions and interlayer spacings.

Demonstrated applicability to bilayer and trilayer graphene.

Abstract

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 their local in-plane structural deformations, twist direction, and out-of-plane structure is needed. In principle, interference in overlap regions of Bragg disks originating from separate layers of a material encodes three-dimensional information about the relative positions of atoms in the corresponding layers. Here, we describe an interferometric four-dimensional scanning transmission electron microscopy technique that utilizes this phenomenon to extract precise structural information from few-layer materials with nm-scale resolution. We demonstrate how this technique enables measurement of local pm-scale in-plane lattice distortions as well as twist direction and average interlayer spacings in bilayer and trilayer graphene, and therefore provides a means to better understand the interplay between electronic properties and precise structural arrangements of few-layer 2D materials.