Coherent x-ray imaging of defects in colloidal crystals

Abstract

Coherent x-ray diffractive imaging ͑CXDI͒ was applied to reveal the structure of colloidal crystals. The colloidal sample was illuminated by a coherent x-ray beam through a 7 m pinhole aperture. The resulting diffraction patterns contain several Bragg peaks and an additional interference structure between the peaks due to the coherent illumination of a finite part of the sample. The inversion of these diffraction patterns reveals the arrangement of colloidal particles in a face-centered cubic ͑fcc͒ lattice as well as defects in the form of stacking faults in the ͑111͒ planes.

Three-dimensional structure of a single colloidal crystal grain studied by coherent x-ray diffraction

“…2(c)). This is similar to observations in our previous experiments on coherent scattering from finite crystals [8,9,11,25]. We can see from this figure that we have sufficient detector resolution (more than five pixels per average fringe) to sample these speckles.…”

“…This is typical for stacking fault defects without the shift of the neighboring atomic planes considered in our model. In the case of a shift of atomic planes additional streaks will appear (compare to results in [11]). Such behavior was not observed in our experiment.…”

“…This method was recently extended to image a finite region of a two-dimensional (2D) colloidal crystal [11]. In this proof-of-principle experiment it was demonstrated that inversion of the coherent diffraction pattern containing several Bragg peaks gives the position of individual scatterers (colloidal spheres in this case) as well as the core structure of the defects in the sample.…”

Coherent Resonant Soft X-ray Scattering Study of Magnetic Textures in FeGe

“…In this situation, the form factor of the object in the lattice is sampled by only a few points in reciprocal space (at the structural Bragg peaks positions) and modulates the intensities of the corresponding peaks. Experimentally, similar results have been unambiguously demonstrated in [5], where exclusion of the higher-order harmonics from the input Fourier-space pattern resulted in the loss of information about the individual shape and size of the nanograins in the photonic crystal superlattice. Therefore, when the measured diffraction pattern is limited in q-space by first-order Bragg peaks, only reconstruction of the pinhole shape and particle positions can be retrieved.…”

“…The method is extremely useful for the structural examination of non-crystalline specimens [1][2][3][4], and can be applied for the determination of the exact positions of individual scattering objects and the mapping of defects in periodically ordered structures [5,6]. One of the promising applications of coherent soft X-rays is the imaging of the local magnetization of magnetic specimens [7].…”