Quantitative 3D imaging of highly distorted micro-crystals using Bragg ptychography

Abstract: Bragg coherent diffraction imaging (BCDI) fails to reliably retrieve phases in micro-crystals exhibiting strong strain inhomogeneities, which restricts its applicability. Here we show that three-dimensional Bragg ptychography (3DBP) overcomes this limitation by enabling stable inversion for large lattice distortions. Using a combination of experimental measurements and numerical tests, we compare the performance limits of the two approaches and demonstrate that 3DBP tolerates lattice distortions more than six times larger than BCDI. We also establish the sensitivity of both methods on a weakly distorted crystal, for which 3DBP yields smoother amplitude and phase fields with reduced short-length-scale artifacts. 3DBP thus provides a reliable route for imaging micro-crystals with large lattice distortions, expanding the scope of coherent X-ray Bragg microscopy to strongly deformed systems.