EBSD for Precise Crystallographic Orientation Mapping of van der Waals Materials

Precise determination of crystallographic orientation is crucial for engineering van der Waals heterostructures, where twist angles control emergent electronic and optical properties. The relative alignment of crystallographic axes gives rise to phenomena such as correlated electronic states and directional photonic responses. While Electron Backscatter Diffraction (EBSD) has been extensively used for bulk materials, its application to van der Waals materials remains largely unexplored. In this work, we demonstrate EBSD as a robust and versatile tool for determining crystallographic orientations of van der Waals materials with high precision. EBSD is a Scanning Electron Microscopy (SEM) based technique that analyzes Kikuchi diffraction patterns from backscattered electrons, enabling mapping of crystal orientation, phase, and grain boundaries at tens of nanometer resolution. We show quantitative agreement between EBSD-determined orientations and facet orientations in MoO₃ flakes on Si substrates. The Grain Reference Orientation Distribution (GROD) and Kernel Average Misorientation (KAM) across the flakes demonstrate an average precision better than 0.1°. We successfully extend this technique to other low-symmetry materials such as WTe₂ and ReSe₂, demonstrating broad applicability across van der Waals materials with varying crystal structures. As a proof-of-concept application, we leverage EBSD-determined orientations to engineer twisted MoO₃ heterostructures with precisely controlled twist angles, enabling observation of the recently reported canalized phonon polaritons. Our results establish EBSD as a powerful characterization method for van der Waals materials, enabling precise orientation control essential for twistronics and twist-optics.