(Invited) Understanding Strain and Deformation in 2D Materials Via 4D-STEM and Cryo-EM

Abstract

Strain and deformations play a critical role in the mechanical, electrical, and chemical properties of two-dimensional (2D) materials due to their atomic thinness. This presentation will discuss using the state-of-the-art transmission electron microscopy (TEM) techniques to study the strain and deformations in 2D materials. First, the speaker will introduce the study of strain relaxation in epitaxial lateral heterojunctions of 2D transition metal dichalcogenides (TMD) using nano-beam four-dimensional scanning TEM (4D-STEM)1. By developing an unsupervised learning approach, we were able to accelerate and automate the method for more general users2. In addition, the speaker will also present the direct visualization of the floppiness of 2D DNA origami using cryo-EM. The work uncovers flexible arms in 2D cross tiles, as well as clusters and stacks, which may potentially affect the assembly of DNA origami3. Han, Y. et al. Strain Mapping of Two-Dimensional Heterostructures with Subpicometer Precision. Nano Letters 18, 3746–3751 (2018).Shi, C. et al. Uncovering material deformations via machine learning combined with four-dimensional scanning transmission electron microscopy. Npj Comput Mater 8, 114 (2022).Ni, H. et al. Direct visualization of floppy two-dimensional DNA origami using cryogenic electron microscopy. Iscience 25, 104373 (2022).