Nonimaging characterization of imperfect single crystals by means of a three-crystal diffractometer for high energy synchrotron radiation

Abstract

A three-crystal diffractometer for synchrotron radiation with energies of 100 keV and higher has been used in a nondispersive setting to map out the distribution of Bragg scattered intensity in the scattering plane with very high resolution. By using perfect silicon crystals in symmetrical Laue geometry for reflection 220 as monochromator and analyzer, respectively, a resolution of ≊2×10−4 Å−1 in the direction parallel to the reciprocal lattice vector G220 and of ≊10−5 Å−1 in the direction perpendicular to G220 has been achieved at high counting rates. As a first example the mosaic structure of a plastically deformed silicon crystal has been characterized with respect to its mosaic distribution and lattice parameter fluctuations. Second, the study of a silicon-germanium gradient crystal, produced by means of the chemical vapor deposition technique, demonstrated that the substrate peak could be well separated from the intensity distribution of the gradient crystal. A two-dimensional contour plot of the intensity distribution in the vicinity of 220 shows the variation of the lattice parameters in the gradient crystal, as well as the lattice plane tilts of the substrate and the silicon-germanium layers.