Diffraction imaging of high quality bismuth silicon oxide with monochromatic synchrotron radiation: Implications for crystal growth

Growth of Sillenite-Structure Single Crystals

“…Melt growth of small (Ӎ8 × 6 × 12 mm) BSO crystals under near-equilibrium conditions [34] shows however that the optical inhomogeneity cannot be explained solely by growth rate instability and anisotropy. Steiner et al [34] suppose that the periodic optical inhomogeneity in faceted crystal growth is associated with deviations from stoichiometry within the homogeneity range of the crystal ---and with the variation in impurity concentration due to small temperature fluctuations.…”

“…Melt growth of small (Ӎ8 × 6 × 12 mm) BSO crystals under near-equilibrium conditions [34] shows however that the optical inhomogeneity cannot be explained solely by growth rate instability and anisotropy. Steiner et al [34] suppose that the periodic optical inhomogeneity in faceted crystal growth is associated with deviations from stoichiometry within the homogeneity range of the crystal ---and with the variation in impurity concentration due to small temperature fluctuations. Note that precision measurements on samples cut from the seed and tail ends of BSO and BGO single crystals about 400 mm in length revealed no differences in density or lattice parameter [13,14], suggesting that both compounds have an insignificant homogeneity range, in contrast to what was reported by Hill and Brice [39].…”

“…Growth defects in BSO and BGO crystals were studied in [34,43,[131][132][133]] by x-ray topography, which revealed well-defined inclusions, striations, and stacking faults. Dislocations in BSO and BGO crystals can be revealed by selective chemical etching [62,134] or annealing in a reducing atmosphere (2-5% H 2 + 98−95% N 2 ) [41,135].…”

High resolution diffraction imaging of crystals grown in microgravity and closely related terrestrial crystals

“…All of these observations are consistent with a growth model in which growth begins in the extreme [110) corner of this crystal (in figure 1, for example, this is the top corner) and proceeds relatively uneventfully in the [110) direction (downward in figure 1, for example), or at least in a direction projected onto this direction in the images, until just before the onset of the wide swath of a high density of additional phase features, one of which initiated the sharp lattice twist visible in figures 9,12,16,19,22,25. This twist then propagated for the remainder of the growth.…”

“…Therefore, indirect: image detectors cannot be used. Although vidicon detectors are used currently to follow image-changes as the incident or glancing angle of an x-ray beam is changed [40], they have never been tested in practice as a means of viewing isolated dislocations. We have used a high-quality GaAs crystal to test the practical applicability of a vidicon detector as a replacement for wet film technology.…”