Full, 3D-resolved lattice strain tensor measurements of specific crystallographic defects extracted from a bulk sample

Lattice defects are key to the deformation behaviour of crystalline materials. Yet studying the 3D lattice strain fields they cause, and which control defect interactions, remains a monumental challenge. Bragg Coherent Diffraction Imaging (BCDI) has emerged as a transformational tool for probing crystal morphology and lattice distortion with nano-scale 3D spatial resolution. However, it is currently limited to materials that readily form micro-crystals. Here we present a new approach, using focussed ion beam (FIB) machining to manufacture micron-sized strain microscopy samples from a macroscopic crystal. The spatial specificity of this technique makes it possible to position pre-selected defects inside the strain microscopy sample, transforming BCDI into a targeted microscopy tool applicable to all crystalline materials. Using this new preparation technique complex 3D dislocation structures in tungsten are studied. For the first time, using a new analysis approach for multi-reflection BCDI data, we are able to recover the full lattice strain tensor in a sample containing multiple dislocations. Our results enable a detailed analysis of the 3D dislocation structure and the associated lattice strains. The ability to reliably image the full nano-scale lattice strain tensor associated with specific microstructural features is anticipated to find applications in materials science, nanoscience, solid-state physics and chemistry.