Correlative 3D Electron Tomography and Nanobeam 4D-STEM Mapping of Orientation and Strain in Welded Silver Nanowires.

A correlative analysis combining three-dimensional (3D) electron tomography and small convergence angle convergent-beam electron diffraction acquired in four-dimensional scanning transmission electron microscopy (4D-STEM) mode is used to investigate the structure, crystallographic orientation, and strain distribution in thermally welded silver nanowire (AgNW) junctions. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) tomography enables reconstruction of the asymmetric and faceted morphology of AgNW welds, revealing distinct ridge continuity and facet-specific junction geometries. Complementary diffraction mapping demonstrates orientation inheritance across the junction and crystallographic continuity within the welded region. Full-field strain maps derived from nanobeam 4D-STEM reveal minimal coherent strain (typically <0.5%) and small rotational distortions associated with nanowire bending. This multidimensional correlation of geometry, crystallography, and strain provides insight into weld formation mechanisms and interfacial behavior beyond the limits of conventional two-dimensional and localized atomic-resolution studies.