Strain Relaxation in Layered Lateral Heterostructures: Insights From Molecular Simulations and Unconventional HAADF‐STEM Imaging

Abstract

A unique relaxation mechanism in wet‐chemically synthesized Bi2Te3–Sb2Te3 lateral heterostructures is presented, combining insights from molecular statics/dynamics simulations with a novel characterization technique based on STEM imaging using a defocused probe. The molecular simulations indicate that these heterostructures undergo intrinsic structural relaxation due to lattice mismatch and elastic anisotropy, resulting in uniform bending into dome‐shaped geometries with radii of curvature on the micron scale. While conventional bright‐field TEM imaging experimentally shows symmetric bend contours due to uniform bending, we demonstrate that defocused HAADF‐STEM produces unique contrast patterns sensitive to the sign of the probe defocus. This allows for the acquisition of crystallographic information (both magnitude and sign of curvature) in real space over large fields of view. The underlying physical mechanism is elucidated through scattering theory, focusing on the matching of the incident electron wave phase front with the local crystal lattice orientation and is supported by comprehensive dynamical multislice simulations of electron channeling maps. These findings are further validated by electron tomography and momentum‐resolved 4D‐STEM experiments. These insights are not only relevant for deciphering the local crystallographic properties of the Bi2Te3–Sb2Te3 system, but also establish a STEM‐based approach to characterize crystal bending across different zone axes in 2D nanostructures. This methodology provides a robust, real‐space alternative for analyzing intrinsic or strain‐induced curvature over large fields of view using unconventional HAADF‐STEM.