Abstract
The growth-induced defect structure of solution-grown crystals of potassium hydrogen phthalate (KAP) has been investigated using synchrotron X-ray diffraction topography. The majority of the crystals examined contained very low defect densities and levels of strain. Dislocation densities typically varied between about 5 and 15cm−2. The strain associated with growth sector boundaries was so low as to render them invisible in most topographic images. All crystals exhibited substantial sectorial variation in the extent of solvent inclusion, with growth sectors at one end of the crystal polar axis incorporating substantially higher levels than the other end. The relationship between the asymmetry of solvent incorporation and that of the growth-induced surface topology of KAP crystals has been examined using ex-situ atomic force microscopy. The dislocation density in most of the crystals studied also showed a pronounced sectorial dependence. A detailed characterization of growth dislocations was carried out. Dislocations with Burgers vectors [001], [100], 〈101〉 and 〈110〉 were observed with [001] being dominant. A substantial proportion of the observed dislocations occurred in pairs which adopted a v-shaped configuration. In some cases, the different line directions of the pair arose from different Burgers vectors for each dislocation of the pair. The divergence of the dislocations in other instances is attributed to nucleation of the pair on a growth sector boundary with each dislocation of the pair lying in a different growth sector and therefore adopting a different line direction.