scholarly journals Grating-based holographic diffraction methods for X-rays and neutrons: phase object approximation and dynamical theory

2018 ◽  
Vol 51 (1) ◽  
pp. 68-75 ◽  
Author(s):  
Hao Feng ◽  
Rana Ashkar ◽  
Nina Steinke ◽  
Robert Dalgliesh ◽  
Nickolay V. Lavrik ◽  
...  
Keyword(s):  
Spin Echo ◽  
Dynamical Theory ◽  
X Rays ◽  
Phase Approximation ◽  
X Ray Diffraction ◽  
Colloidal Structure ◽  
X Ray ◽  
X Ray Scattering ◽  
Weak Phase ◽  
Colloidal Fluids

A method dubbed grating-based holography was recently used to determine the structure of colloidal fluids in the rectangular grooves of a diffraction grating from X-ray scattering measurements. Similar grating-based measurements have also been recently made with neutrons using a technique called spin-echo small-angle neutron scattering. The analysis of the X-ray diffraction data was done using an approximation that treats the X-ray phase change caused by the colloidal structure as a small perturbation to the overall phase pattern generated by the grating. In this paper, the adequacy of this weak phase approximation is explored for both X-ray and neutron grating holography. It is found that there are several approximations hidden within the weak phase approximation that can lead to incorrect conclusions from experiments. In particular, the phase contrast for the empty grating is a critical parameter. While the approximation is found to be perfectly adequate for X-ray grating holography experiments performed to date, it cannot be applied to similar neutron experiments because the latter technique requires much deeper grating channels.

Investigation of the phase shift in X-ray forward diffraction using an X-ray interferometer

1998 ◽  
Vol 5 (3) ◽  
pp. 967-968 ◽  
Author(s):  
Keiichi Hirano ◽  
Atsushi Momose
Keyword(s):  
Phase Shift ◽  
Silicon Crystal ◽  
Dynamical Theory ◽  
Perfect Crystal ◽  
X Rays ◽  
X Ray Diffraction ◽  
X Ray ◽  
Bragg Geometry

The phase shift of forward-diffracted X-rays by a perfect crystal is discussed on the basis of the dynamical theory of X-ray diffraction. By means of a triple Laue-case X-ray interferometer, the phase shift of forward-diffracted X-rays by a silicon crystal in the Bragg geometry was investigated.

An algorithm for calculating diffraction profiles of 2θ scans for multiple diffraction from crystals and thin films

2014 ◽  
Vol 70 (6) ◽  
pp. 572-582
Author(s):  
Hsin-Yi Chen ◽  
Mau-Sen Chiu ◽  
Chia-Hung Chu ◽  
Shih-Lin Chang
Keyword(s):  
Initial Phase ◽  
Atomic Layer ◽  
Dynamical Theory ◽  
Far Field ◽  
X Rays ◽  
X Ray Diffraction ◽  
Multiple Diffraction ◽  
X Ray ◽  
Beam Surface ◽  
Surface Diffraction

An algorithm is developed based on the dynamical theory of X-ray diffraction for calculating the profiles of the diffracted beam,i.e.the diagrams of the intensity distributionversus2θ when a crystal is fixed at an angle of its maximum diffracted intensity. Similar to Fraunhofer (far-field) diffraction for a single-slit case, in the proposed algorithm the diffracted beam from one atomic layer excited by X-rays is described by the composition of (N+ 1) coherent point oscillators in the crystal. The amplitude and the initial phase of the electric field for each oscillator can be calculated based on the dynamical theory with given boundary conditions. This algorithm not only gives diffraction profiles but also provides the contribution of the excitation of modes when extremely asymmetric diffraction is involved in the diffraction process. Examples such as extremely asymmetric two-beam surface diffraction and three-beam surface diffraction are presented and discussed in detail.

scholarly journals Experimentally obtained and computer-simulated X-ray non-coplanar 18-beam pinhole topographs for a silicon crystal

2019 ◽  
Vol 75 (3) ◽  
pp. 483-488 ◽  
Author(s):  
Kouhei Okitsu ◽  
Yasuhiko Imai ◽  
Yoshitaka Yoda
Keyword(s):  
Silicon Crystal ◽  
Dynamical Theory ◽  
X Rays ◽  
X Ray Diffraction ◽  
X Ray ◽  
Good Agreement

Non-coplanar 18-beam X-ray pinhole topographs for a silicon crystal were computer simulated by fast Fourier transforming the X-ray rocking amplitudes that were obtained by solving the n-beam (n = 18) Ewald–Laue dynamical theory (E-L&FFT method). They were in good agreement with the experimentally obtained images captured using synchrotron X-rays. From this result and further consideration based on it, it has been clarified that the X-ray diffraction intensities when n X-ray waves are simultaneously strong in the crystal can be computed for any n by using the E-L&FFT method.

Dynamical effects in the integrated X-ray scattering intensity from imperfect crystals in Bragg diffraction geometry. I. Semi-dynamical model

2020 ◽  
Vol 76 (1) ◽  
pp. 45-54
Author(s):  
V. B. Molodkin ◽  
S. I. Olikhovskii ◽  
S. V. Dmitriev ◽  
A. I. Nizkova ◽  
V. V. Lizunov
Keyword(s):  
Silicon Crystal ◽  
Azimuthal Angle ◽  
Dynamical Theory ◽  
Bragg Diffraction ◽  
X Ray Diffraction ◽  
X Ray ◽  
X Ray Scattering ◽  
Diffraction Geometry ◽  
Coulomb Type ◽  
Analytical Expressions

The analytical expressions for the coherent and diffuse components of the integrated reflection coefficient are considered in the case of asymmetric Bragg diffraction geometry for a single crystal of arbitrary thickness, which contains randomly distributed Coulomb-type defects. The possibility to choose the combinations of diffraction conditions optimal for characterizing defects of several types by accounting for dynamical effects in the integrated coherent and diffuse scattering intensities, i.e. primary extinction and anomalous absorption, has been analysed based on the statistical dynamical theory of X-ray diffraction by imperfect crystals. The measured integrated reflectivity dependencies of the imperfect silicon crystal on azimuthal angle were fitted to determine the diffraction parameters characterizing defects in the sample using the proposed formulas in semi-dynamical and semi-kinematical approaches.

scholarly journals Carbon clusters formed from shocked benzene

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
D. M. Dattelbaum ◽  
E. B. Watkins ◽  
M. A. Firestone ◽  
R. C. Huber ◽  
R. L. Gustavsen ◽  
...  
Keyword(s):  
High Pressures ◽  
Complex Mixture ◽  
Carbon Clusters ◽  
X Rays ◽  
Reaction Products ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Liquid Benzene ◽  
X Ray Scattering

AbstractBenzene (C6H6), while stable under ambient conditions, can become chemically reactive at high pressures and temperatures, such as under shock loading conditions. Here, we report in situ x-ray diffraction and small angle x-ray scattering measurements of liquid benzene shocked to 55 GPa, capturing the morphology and crystalline structure of the shock-driven reaction products at nanosecond timescales. The shock-driven chemical reactions in benzene observed using coherent XFEL x-rays were a complex mixture of products composed of carbon and hydrocarbon allotropes. In contrast to the conventional description of diamond, methane and hydrogen formation, our present results indicate that benzene’s shock-driven reaction products consist of layered sheet-like hydrocarbon structures and nanosized carbon clusters with mixed sp2-sp3 hybridized bonding. Implications of these findings range from guiding shock synthesis of novel compounds to the fundamentals of carbon transport in planetary physics.

Limits of the X-Ray Collimation by One Asymmetrical Bragg Reflection

1982 ◽  
Vol 37 (6) ◽  
pp. 519-523 ◽  
Author(s):  
◽  
H. R. Höche ◽  
J. Nieber
Keyword(s):  
Bragg Reflection ◽  
Dynamical Theory ◽  
X Rays ◽  
Optimum Conditions ◽  
X Ray Diffraction ◽  
X Ray

Abstract In connection with the production of highly collimated X-rays the study of extremely asymmetrical Bragg reflections became of interest. In this paper the so-called extended dynamical theory of X-ray diffraction will be tested experimentally. As a result of this investigations the optimum conditions for X-ray collimation by means of one asymmetrical Bragg reflection are being discussed.

Laue X-ray diffraction studies of the structural perfection of Al-doped thermomigration channels in silicon

2021 ◽  
Vol 54 (2) ◽  
pp. 588-596
Author(s):  
Andrey A. Lomov ◽  
Vasily I. Punegov ◽  
Boris M. Seredin
Keyword(s):  
Cross Sections ◽  
High Sensitivity ◽  
Dynamical Theory ◽  
X Rays ◽  
X Ray Diffraction ◽  
Structural Perfection ◽  
Laue Diffraction ◽  
X Ray ◽  
Structural Distortions ◽  
Further Development

Si(111) wafers patterned with an array of vertical 100 µm-wide Al-doped (1 × 1019 cm−3) p-channels extending through the whole wafer were studied by X-ray Laue diffraction techniques. The X-ray techniques included projection topography, and measurement of rocking curves and cross sections in the vicinity of the 02\overline 2 reciprocal space node in the double- and triple-crystal geometry, respectively. The channels are uniform along the depth of the wafer, and their structural perfection is comparable to that of the silicon matrix between the channels. Simulation of the rocking curves was performed using the methods of the dynamical theory of X-ray diffraction. The rocking-curve calculations both taking into account and neglecting the effect of the instrumental function were carried out using the Takagi–Taupin equations. The calculated angular dependences of intensities of both diffracted and transmitted X-rays correspond well to the experimentally obtained rocking curves and demonstrate their high sensitivity to the structural distortions in the channel. An unambiguous reconstruction of strain and structural distortions in the Si(Al) channel using the Laue diffraction data requires further development of the theoretical model.

Book Reviews: The gentle pioneer

1996 ◽  
Vol 50 (2) ◽  
pp. 263-264
Keyword(s):  
Modern Science ◽  
Mathematical Physics ◽  
Dynamical Theory ◽  
X Rays ◽  
Experimental Demonstration ◽  
X Ray Diffraction ◽  
International Union ◽  
X Ray ◽  
Oxford University

P.P. Ewald and his Dynamical Theory of X-ray Diffraction . Edited by D.W.J. Cruickshank, H.J. Juretschke & N. Kato. International Union of Crystallography, Oxford University Press, 1992. Pp. x+161, £40.00. ISBN 0-19-855379-X Paul Ewald, who died in 1985 at the age of 97, was one of the greats of modern science. Born in Berlin into a comfortable middle-class academic family, he developed a passion for mathematical physics. When Sommerfeld presented him with a list of possible topics for his Doctoral Thesis he chose one related to crystal optics. This work, presented in 1912, could be applied to the behaviour of X-rays in crystals and it is suggested that it was a conversation between von Laue and Ewald early in 1912 that gave von Laue the idea for his famous experimental demonstration of X-ray diffraction.

Towards high-flux X-ray beam compressing channel-cut monochromators

2016 ◽  
Vol 49 (6) ◽  
pp. 1885-1892 ◽  
Author(s):  
Karol Végsö ◽  
Matej Jergel ◽  
Peter Šiffalovič ◽  
Eva Majková ◽  
Dušan Korytár ◽  
...  
Keyword(s):  
Compression Ratio ◽  
Single Point ◽  
Grazing Incidence ◽  
High Flux ◽  
X Rays ◽  
X Ray Diffraction ◽  
X Ray ◽  
X Ray Scattering ◽  
Medium Resolution ◽  
Experimental Resolution

The issue of a high-flux X-ray beam compressing channel-cut monochromator for applications in X-ray metrology is addressed. A Ge(111) compressor with compression ratio 20.3 was designed on the principle of a combination of symmetric and highly asymmetric diffractions. A pilot application of the single-point diamond technology (SPDT) to finish active surfaces of X-ray optics was tested, providing 50% flux enhancement as compared to a Ge(220) counterpart prepared by traditional surface treatment. This is much more than the theoretical 22% forecast and shows the potential of SPDT for preparation of high-flux X-ray compressors with a high compression ratio, where highly asymmetric diffraction with a very low exit angle is inevitable. The implications for efficient collection of X-rays from microfocus X-ray sources are discussed. A comparison of Ge compressors with Ge parallel channel-cut monochromators combined with a 50 µm slit shows the several times higher flux of the former, making them applicable in X-ray diffraction experiments at medium resolution. Furthermore, the Ge(111) compressor was tested as a collimator in high-resolution grazing-incidence small-angle X-ray scattering (GISAXS) measurements of surface gratings, providing experimental resolution close to 400 nm. This is ∼100 nm smaller than that achieved with the Ge(220) compressor but still approximately twice that of commercial SAXS/GISAXS laboratory setups.

X-ray Scattering from Interfaces

1991 ◽  
Vol 237 ◽  
Author(s):  
E. Vlieg ◽  
H. A. Van Der Vegt
Keyword(s):  
Epitaxial Growth ◽  
Surface Structures ◽  
X Rays ◽  
X Ray Diffraction ◽  
General Outline ◽  
X Ray ◽  
Buried Interfaces ◽  
X Ray Scattering ◽  
High Penetration

ABSTRACTX-ray diffraction has found an increasing use in the characterization of surface structures. Due to the high penetration depth of X-rays, the technique is also very suitable for the study of buried interfaces. We will give a general outline of the technique, and then discuss two examples concerning epitaxial growth.

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