Synchrotron x-ray reticulography: principles and applications

Synchrotron x-ray reticulography is a versatile new technique for mapping m isorientations in single crystals. It is nearly as simple to perform as con ventional single-crystal Laue topography, yet it yields quantitative data o n misorientations that would demand long sequences of images if the double- crystal technique were applied. In reticulography a fine-scale x-ray absorb ing mesh is placed between a Laue-diffracting crystal specimen and the topo graph-recording photographic plate. The mesh splits the diffracted beam int o an array of individually identifiable microbeams. Direction differences b etween microbeams, which give the orientation differences between the cryst al elements reflecting them, are measured from their relative shifts within the array when mesh-to-plate distance is changed. The angular sensitivity of reticulography depends upon the angular size of the x-ray source. At Sta tion 7.6 at the SRS, Daresbury, 80 m from the tangent point, and with sourc e size FWHM (full width half maximum) = 0.23 mm vertically, the incidence a ngular range in the vertical plane is only 0.6 arcsec, and misorientations down to this magnitude are measurable. Applications of reticulography to th ree quite different problems are described, illustrating the method's versa tility. The problems are: (1) measuring surface lattice-plane tilts due to an array of dislocations in a large synthetic diamond; (2) determining the sense of the Burgers vector of a giant screw dislocation in SiC; and (3) me asuring lattice curvature above an energetic ion implant in a natural diamo nd.