On the variation of X-ray diffraction contrast with wavelength: A study with synchrotron radiation

Abstract

Diffraction contrast phenomena on X-ray topographs taken with continuous-spectrum synchrotron radiation have been studied at wavelengths of 0.057, 0.064, 0.071, 0.100, 0.154, 0.206 and 0.250 nm. The specimen was a polished plate of natural diamond with surfaces parallel to (110), ½ mm thick. Using the {\bar 1}11 reflection and a stored electron beam energy of 1.8 GeV all topographs (except that taken with λ = 0.25 nm) were harmonic free. The specimen exhibited mixed-habit growth, containing sectors of normal faceted {111} growth and sectors of non-faceted `cuboid' growth in which growth-surface orientation was variable and only approximately parallel to {100}. Prior to X-ray topography the specimen had received localized damage from implantation with fluorine ions of 17 MeV energy. Features whose variation with wavelength was studied included (1) the relative strengths of integrated reflections from {111} and `cuboid' growth sectors, (2) the intensity of `spike' disorder diffuse reflections relative to sharp Bragg reflections, (3) contrast from inclusions, polishing striae and fracture damage and (4) lattice bending and diffraction contrast at the sites of fluorine ion implantation. Theoretical predictions of the wavelength variation of the intensity of the diffuse reflection images and of contrast due to resolved defects showed good agreement with the observations.