Plastic Deformation of InSb Micro-Pillars: A Comparative Study Between Spatially Resolved Laue and Monochromatic X-Ray Micro-Diffraction Maps

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X-ray Coherent diffraction interpreted through the fractional Fourier transform

Diffraction of coherent x-ray beams is treated through the Fractionnal Fourier transform. The transformation allow us to deal with coherent diffraction experiments from the Fresnel to the Fraunhofer regime. The analogy with the Huygens-Fresnel theory is first discussed and a generalized uncertainty principle is introduced.Comment: 7 pages, 8 figure

White light-induced halide segregation in triple-cation mixed halide perovskites studied by in-situ fast scanning nano-XRF at the NANOSCOPIUM beamline, Synchrotron SOLEIL

International audienceAbstract In-situ study of the variation of the chemical composition of triple-cation mixed halide perovskites Cs 0.05 (MA 0.17 FA 0.83 ) 0.95 Pb(I 0.83 Br 0.17 ) 3 under visible light illumination performed by Fast Scanning Nano Hard X-ray Fluorescence Imaging revealed the migration and irreversible phase separation of halide ions into micro-meter sized clusters

Pinning and depinning process of an incommensurate CDW as revealed by coherent X-ray diffraction

International audienceExperiments on the coherent X-ray diffraction, and their modeling, have been performed on the Charge Density Wave (CDW) system NbSe3. The 2k(F) satellite reflection associated with the CDW has been measured with respect to external dc currents. Below the threshold current, reflection displays several fringes in the transverse direction which disappear when the threshold current is exceeded. In the sliding state, the transverse satellite profile has a form of two nonsymmetric peaks, one of them being centered at the same position as below the threshold and another one being shifted. The shift of the longitudinal peak position below the threshold current and the nonsymmetric peak in the transverse direction above the threshold one is interpreted as the influence of strong linear defect like a crystal step present on the sample surface, combined with induced arrays of dislocations. Coherent X-rays provide a new access to processes in a CDW driven by an external force in a random pinning potential

Evolution of a large-periodicity soliton lattice in a current-driven electronic crystal

International audienceWe report here on a detailed coherent x-ray diffraction study of the charge-density wave in K0.3MoO3 as a function of an external current. At threshold current, the charge-density wave undergoes a strong decrease of average amplitude keeping large correlation lengths. At the same time, an extra electronic modulation with large periodicity appears directly related to the sliding of the charge-density wave. This effect is interpreted as the formation of a soliton lattice and its evolution with respect to external current is investigated. The charge-density wave phase is found to undergo an anharmonic to harmonic transition when a current is injected

Bulk Dislocation Core Dissociation Probed by Coherent X Rays in Silicon

International audienceWe report on a new approach to probe bulk dislocations by using coherent x-ray diffraction. Coherent x rays are particularly suited for bulk dislocation studies because lattice phase shifts in condensed matter induce typical diffraction patterns which strongly depend on the fine structure of the dislocation cores. The strength of the method is demonstrated by performing coherent diffraction of a single dislocation loop in silicon. A dissociation of a bulk dislocation is measured and proves to be unusually large compared to surface dislocation dissociations. This work opens a route for the study of dislocation cores in the bulk in a static or dynamical regime, and under various external constraint

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Evidence of charge density wave transverse pinning by x-ray microdiffraction

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New long-range sub-structure found in the tetragonal phase of CH3NH3PbI3 single crystals

International audienceHybrid organic-inorganic perovskites have become one of the most promising low-cost alternatives to traditional semiconductors in the field of photovoltaics and light emitting devices. It combines both attractive features of organic and inorganic materials within a single composite, for instance with excellent electronic properties. We used x-ray diffraction to reveal a sub-structure within CH 3 NH 3 PbI 3 single crystals. We could observe the presence of additional peaks with a square symmetry in several monocrystalline samples. We discuss these results in terms of two different models: a superstructure modulated in two in-plane orthogonal directions, and a model with tilted domains with a shallow angle of ~0.6°. In both cases, the modulated or tilted domains appear in regions with small lattice expansion. We show that this last model appears to be the most likely to explain our observations