Schematic of experimental setup for section topography. Stripe-shaped beam was obtained by limiting the height of incident white x-ray with a slit. The stripe-shaped white x-ray is diffracted by high-quality -SiC with a diffraction vector . Owing to white x-ray, the Bragg condition can be satisfied even on the lattice plane distorted by a screw dislocation. The redshifted and blueshifted beam diffracted on the distorted lattice plane near the screw dislocation deviates with a minute angle compared to that far from the dislocation. The small angular dispersion of the diffracted beam can be detected on a film (nuclear plate) placed at a distance of from the sample.
Synchrotron white x-ray topographs, projection topograph (a) and section topograph (b) obtained at the broken line of (a). (c) is a synchrotron monochromatic x-ray topograph taken at the same area as (a) (white area on the left edge is due to shading diffracted beam by a sample holder). (d) is a simplified schematic of (a), in which right-handed and left-handed dislocations are indicated by black and white, respectively.
Magnified image of section topograph of Fig. 2(b). The screw dislocation that originates from this hyperbolic profile is right handed. Theoretical hyperbolic curves for the Burgers vectors of , , , and are also drawn on the observed section topograph. It is clear that the curve for best fits the experimental profile.
Section topograph of in width. Right-handed and left-handed dislocations are marked with and , respectively. Regions with closely spaced screw dislocations are denoted by asterisk. Broken arrows indicate connections of the original section topograph.
Histograms for the spacing between two adjacent screw dislocations with opposite senses (a) and with the same senses (b). It can be recognized that two adjacent screw dislocations with the opposite senses strongly tend to have small spacing under , while the two adjacent screw dislocations with the same senses.
Dislocation-image width dependences on tilt angle of dislocation line from (a). The inset in (a) is a geometry for a ray-tracking simulation. Schematic illustrations of bimodal and unimodal image formation mechanism at the tilt angle of 90° are drawn on the top and bottom of (b), respectively.
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