Synchrotron X-ray microdiffraction measurements of lattice tilts within CVD diamond crystallites terminated by cathodoluminescent blue-cross-quartered cube facets

A [001]-textured microwave plasma CVD diamond film contains crystallites wi th large square (001) facets, edge lengths up to similar to 100 mu m, that have attracted attention because of an unusual highly symmetric step patter n on these (001) facets. This pattern consists of arrays of steps (heights in the 10-20-nm range) facing inwards from the facet corners towards the fa cet centre, thereby dividing the facet surface into quadrants with a rough mirror symmetry in (110) and (1 (1) over bar 0); and these dividing mirror planes are also loci of blue-violet cathodoluminescent emission, the "Blue- Cross". The present work has applied synchrotron X-ray microradiography as a high-contrast imaging technique for displaying size and habit distributio n in the crystallite population, and microdiffraction and topography for me asuring misorientations within chosen individual crystallites. Studies of t he microscopically observed step patterns, surface tilt profiles and X-ray diffraction pattern fine structure are detailed for two crystallites, one b eing in the largest size bracket, facet diameter 91 mu m, and the other of a more common size, facet diameter 53 mu m. X-ray diffraction data corrobor ated and amplified findings made in previous work by electron channelling p atterns. The X-ray diffraction patterns strikingly demonstrated that the cr ystal lattice under the (001) facet has a fourfold split, the normals to th e (001) lattice planes in each quadrant being tilted outward towards the fa cet corner cube direction of the quadrant concerned. Approximate values of the mean outward tilt of the quadrants, relative to the mean [001] axis of the crystallite, were 0.85 degrees in the larger crystallite and 0.4 degree s in the smaller crystallite. (C) 1998 Elsevier Science S.A. All rights res erved.