Aligning van der Waals Heterostructures Using Electron Backscatter Diffraction.

Precise and accurate determination of crystallographic orientation is crucial for engineering van der Waals heterostructures, where the twist angle between layers controls emergent electronic and optical properties. 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. We show quantitative agreement between EBSD-determined orientations and facet orientations in orthorhombic α-MoO3 flakes on silicon substrates. We use kernel average misorientation and grain reference orientation distribution across the flakes to demonstrate angular precision better than 0.2°. We extend this technique to other low-symmetry materials, specifically, monoclinic α-As2Te3, monoclinic GaTe, and triclinic ReSe2, demonstrating broad applicability across van der Waals materials with different crystal structures. Finally, as a proof-of-concept application, we leverage EBSD-determined orientations to engineer a twisted α-MoO3 heterostructure with precisely controlled twist angle, enabling observation of 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 twistoptics.