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1.  High-resolution study of (002, 113, 11−1) four-beam diffraction in Si 
A high-resolution study of (002, 113, 11−1) four-beam diffraction in Si was performed both experimentally and theoretically. Excellent coincidence between theory and experiment was achieved. The forbidden two-beam 002 reflection was excited with the maximum reflectivity of 80%.
The results of a high-resolution study of the (002, 113, ) four-beam diffraction in Si are presented. The incident synchrotron radiation beam was highly monochromated and collimated with a multi-crystal arrangement in a dispersive setup in both vertical and horizontal planes, in an attempt to experimentally approach plane-wave incident conditions. The Renninger scheme was used with the forbidden reflection reciprocal-lattice vector 002 normal to the crystal surface. The azimuthal and polar rotations were performed in the crystal surface plane and the vertical plane correspondingly. The polar angular curves for various azimuthal angles were measured and found to be very close to theoretical computer simulations, with only a small deviation from the plane monochromatic wave. The effect of the strong two-beam 002 diffraction was observed for the first time with the maximum reflectivity close to 80%. The structure factor of the 002 reflection in Si was experimentally determined as zero.
doi:10.1107/S0108767312012305
PMCID: PMC3329769  PMID: 22514065
X-ray multiple diffraction; silicon; high resolution; forbidden reflections
2.  High-resolution study of (222, 113) three-beam diffraction in Ge 
Good agreement between the high-resolution experimental results for (222, 113) three-beam diffraction in Ge and computer simulations based on the dynamical multiple diffraction theory are presented.
The results of high-resolution analysis of the (222, >113) three-beam diffraction in Ge are presented. For monochromatization and angular collimation of the incident synchrotron beam a multi-crystal arrangement in a dispersive setup in both vertical and horizontal planes was used in an attempt to experimentally approach plane-wave incident conditions. Using this setup, for various azimuthal angles the polar angular curves which are very close to theoretical computer simulations for the plane monochromatic wave were measured. The effect of the strong two-beam 222 diffraction was observed for the first time with the maximum reflectivity close to 60% even though the total reflection of the incident beam into a forbidden reflection was not achieved owing to absorption. The structure factor of the 222 reflection in Ge was experimentally determined.
doi:10.1107/S0108767311015261
PMCID: PMC3121237  PMID: 21694480
dynamical diffraction; multiple diffraction; synchrotron radiation; plane waves; X-ray optics
3.  High-resolution study of dynamical diffraction phenomena accompanying the Renninger (222/113) case of three-beam diffraction in silicon 
The effect of the total reflection of the incident beam into the 222 reflected beam in the Renninger (222/113) case in Si was experimentally observed by using a highly monochromatic beam with high angular collimation in both the vertical and horizontal planes.
X-ray optical schemes capable of producing a highly monochromatic beam with high angular collimation in both the vertical and horizontal planes have been evaluated and utilized to study high-resolution diffraction phenomena in the Renninger (222/113) case of three-beam diffraction in silicon. The effect of the total reflection of the incident beam into the nearly forbidden reflected beam was observed for the first time with the maximum 222 reflectivity at the 70% level. We have demonstrated that the width of the 222 reflection can be varied many times by tuning the azimuthal angle by only a few µrad in the vicinity of the three-beam diffraction region. This effect, predicted theoretically more than 20 years ago, is explained by the enhancement of the 222 scattering amplitude due to the virtual two-stage 000 113 222 process which depends on the azimuthal angle.
doi:10.1107/S0108767310010433
PMCID: PMC2891002  PMID: 20555185
dynamical diffraction; multiple diffraction; X-ray optics; plane wave; synchrotron radiation
4.  Spatial structure of a focused X-ray beam diffracted from crystals 
Journal of Synchrotron Radiation  2009;16(Pt 5):666-671.
The spatial structure of an X-ray beam focused by a planar refractive lens and Bragg diffracted from perfect silicon crystals has been studied experimentally and theoretically.
The spatial structure of a beam focused by a planar refractive lens and Bragg diffracted from perfect silicon crystals was experimentally studied at the focal plane using a knife-edge scan and a high-resolution CCD camera. The use of refractive lenses allowed for a detailed comparison with theory. It was shown that diffraction leads to broadening of the focused beam owing to the extinction effect and, for a sufficiently thin crystal, to the appearance of a second peak owing to reflection from the back surface. It was found that the spatial structure of the diffracted beam depends on whether the crystal diffracts strongly (dynamically) or weakly (kinematically). The results help to understand the physical origin of the diffracted intensity recorded in a typical microbeam diffraction experiment.
doi:10.1107/S0909049509029860
PMCID: PMC2733878  PMID: 19713641
X-rays; focusing; refractive lenses; X-ray diffraction; extinction effect

Results 1-4 (4)