Microfocusing transfocator for 1D and 2D compound refractive lenses

Zozulya, Alexey; Бондаренко, С. В.; Schavkan, Alexander; Westermeier, Fabian; Grübel, G.; Sprung, Michael

doi:10.1364/oe.20.018967

Cited by 59 publications

(46 citation statements)

References 25 publications

(29 reference statements)

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“…A monochromatic coherent x-ray beam of 8 keV photon energy was focused at the sample at 87.7 m from the undulator source using the transfocator optics [49] based on compound refractive lenses (CRLs) positioned at 2.2 m distance upstream from the sample (see Fig. 1).…”

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Revealing Three-Dimensional Structure of an Individual Colloidal Crystal Grain by Coherent X-Ray Diffractive Imaging

et al. 2016

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We present results of a coherent x-ray diffractive imaging experiment performed on a single colloidal crystal grain. The full three-dimensional (3D) reciprocal space map measured by an azimuthal rotational scan contained several orders of Bragg reflections together with the coherent interference signal between them. Applying the iterative phase retrieval approach, the 3D structure of the crystal grain was reconstructed and positions of individual colloidal particles were resolved. As a result, an exact stacking sequence of hexagonal close-packed layers including planar and linear defects were identified. DOI: 10.1103/PhysRevLett.117.138002 Colloidal crystals nowadays are actively exploited as an important model system to study nucleation phenomena in freezing, melting, and solid-solid phase transitions [1][2][3][4][5], jamming and glass formation [6,7]. In addition, colloidal crystals are attractive for multiple applications since they can be used as large-scale templates to fabricate novel materials with unique optical properties such as the full photonic band gap, "slow" photons and negative refraction, as well as materials for application in catalysis, biomaterials, and sensorics [8][9][10][11]. Colloidal crystals grown by self-organization provide a low cost large-scale alternative to lithographic techniques, which are very effective for producing high-quality materials with a desired structure, but are limited in building up a truly three-dimensional (3D) structure and bring high production costs [12]. Recently, significant progress has been achieved in engineering materials with tunable periodic structure on the mesoscale by functionalizing colloids with DNA [13], applying external fields [14,15] or varying the particle shape [16,17].Understanding the real structure of colloidal crystals and its disorder is an important aspect from both fundamental and practical points of view. Even at equilibrium, colloidal crystals can have a finite density of defects, which can be anomalously large for certain colloidal lattices [18]. The opposite can also happen as defects can play a decisive role in the choice of the crystal structure [19,20]. For applications such as photonic crystals most of growth-induced defects can deteriorate their optical properties. On the other hand, controlled incorporation of certain defects can be desirable to enhance the functionality such as creating wave guides [21,22], trapping photons [12,23], and developing optical chips [24]. In these studies, monitoring an internal 3D structure of colloidal crystals including defects in real time remains a challenge [25].Among widely used techniques of the colloidal crystal structure investigation are optical microscopy [26,27] and confocal laser scanning microscopy [28]. However, the range of applications of these methods is strongly reduced by the limited resolution (at best about 250 nm) and the need of a careful refractive index matching, which is not always possible. Furthermore, some of the materials are opaque for visible light which comp...

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Revealing Three-Dimensional Structure of an Individual Colloidal Crystal Grain by Coherent X-Ray Diffractive Imaging

et al. 2016

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“…1(a)] was performed at the coherence beamline P10 of the PETRA III facility at DESY. The x rays with the photon energy of 13 keV were focused by compound refractive lenses (CRLs) [20,21] to a spot about 3 μm (FWHM) at the sample. A 2D detector (Pilatus 1M with 981 × 1043 pixels and a pixel size of 172 × 172 μm 2 ) was positioned at 263 mm distance downstream from the sample.…”

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X-ray cross-correlation analysis of liquid crystal membranes in the vicinity of the hexatic-smectic phase transition

et al. 2013

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We present an x-ray study of liquid crystal membranes in the vicinity of the hexatic-smectic phase transition by means of angular x-ray cross-correlation analysis. By applying two-point angular-intensity cross-correlation functions to the measured series of diffraction patterns the parameters of bond-orientational (BO) order in hexatic phase were directly determined. The temperature dependence of the positional correlation lengths was analyzed as well. The obtained correlation lengths show larger values for the higher-order Fourier components of BO order. These findings indicate a strong coupling between BO and positional order. About 30 years ago it was realized that the phase transition between a two-dimensional (2D) crystal and the liquid phase can proceed through an intermediate hexatic phase [1]. The corresponding mechanism involves dissociation of dislocation pairs. The 2D hexatic phase is characterized by a sixfold quasilong-range bond-orientational (BO) order, while the positional order is short range and the shear modulus is zero. Phases with hexatic order have been found in several systems, such as electrons at the surface of helium [2], charged polymer colloids [3,4], and smectic liquid crystals (LCs) [5][6][7]. In the last case a hexatic phase was experimentally observed quite unexpectedly in three-dimensional (3D) stacked molecular systems [8]. In the 3D hexatic phase the positional order is short range, while the BO order persists over a long range. However, the mere existence of a hexatic phase does not imply a specific melting mechanism, and the origin of hexatic order and its relation to the defect-mediated melting transition is still controversial. Smectic liquid crystals are particularly suitable to investigate these problems, as they can be suspended over an opening in a solid frame. Such smectic membranes are substrate-free and have a controlled thickness ranging from two to more than thousands of layers [9].Smectic-A membranes can be described as stacks of liquid layers. The in-plane structure is liquidlike with positional correlations between the molecules decaying exponentially with a correlation length ξ 0 . While cooling a hexatic phase may occur, which shows a long-range BO order. This leads to a sixfold rotational symmetry and the BO correlations are characterized by the local ordering field ψ(r) ∝ exp[i6θ (r)], where θ (r) is the angle between the "bonds" and some reference axis. Upon decreasing the temperature, the width of the radial-intensity peak decreases simultaneously with a further development of the BO order. This indicates a coupling * Present address: The University of California, San Diego, La Jolla, CA 92093, USA.† Corresponding author: ivan.vartaniants@desy.de between the positional correlations and the BO order [10]. Additionally, at even lower temperatures a 3D crystalline phase appears with a hexagonal in-plane lattice or a rectangular lattice with a so-called herringbone order [6,7]. The common way to study the BO order is to perform x-ray or electron diffraction me...

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“…The experiments were performed at beamline P10 of PETRA III at DESY, Germany, 39 at a photon energy of 8.05 keV corresponding to a wavelength of l = 0.15 nm. To obtain a transversally coherent X-ray beam and a sufficient small speckle size in the detector plane, a set of slits upstream of the rheometer reduced the beamsize to typically 20 Â 20 mm 2 to 30 Â 30 mm 2 for coherent X-ray scattering experiments.…”

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confidence: 99%

Connecting structure, dynamics and viscosity in sheared soft colloidal liquids: a medley of anisotropic fluctuations

et al. 2016

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Structural distortion and relaxation are central to any liquid flow. Their full understanding requires simultaneous probing of the mechanical as well as structural and dynamical response. We provide the first full dynamical measurement of the transient structure using combined coherent X-ray scattering and rheology on electrostatically interacting colloidal fluids. We find a stress overshoot during the start-up of shear which is due to the strong anisotropic overstretching and compression of nearest-neighbor distances. The rheological response is reflected in uncorrelated entropy-driven intensity fluctuations.While the structural distortion under steady shear is well described by Smoluchowski theory, we find an increase of the particle dynamics beyond the trivial contribution of flow. After the cessation of shear, the full fluid microstructure and dynamics are restored, both on the structural relaxation timescale. We thus find unique structure-dynamics relations in liquid flow, responsible for the macroscopic rheological behavior of the system.

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Microfocusing transfocator for 1D and 2D compound refractive lenses

Cited by 59 publications

References 25 publications

Revealing Three-Dimensional Structure of an Individual Colloidal Crystal Grain by Coherent X-Ray Diffractive Imaging

Revealing Three-Dimensional Structure of an Individual Colloidal Crystal Grain by Coherent X-Ray Diffractive Imaging

X-ray cross-correlation analysis of liquid crystal membranes in the vicinity of the hexatic-smectic phase transition

Connecting structure, dynamics and viscosity in sheared soft colloidal liquids: a medley of anisotropic fluctuations

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