Dislocation Generation by Microparticle Inclusions

Microscopic inclusions are common sources of dislocations in solution-grown crystals, but the correspondence between the size and shape of inclusions and the probability of dislocation generation has not been established quantitatively. This correspondence is obtained herein through the use of spherical poly(styrene) particles with well-defined diameters, ranging from 1 to 90 μm, which were incorporated within potassium hydrogen phthalate crystals during growth from solution. The probability of generating dislocations by particle overgrowth increased with increasing supersaturation and particle size. The largest particles generate so many dislocations that daughter crystals emerge that are no longer in single-crystal register with the host. The results are consistent with a model that depends on surmounting the elastic energy of crystal layers associated with bending. Dislocation generation during the last stages of overgrowth is favored when the height difference between the growing layer and the particle protruding from the crystal surface is larger than a dislocation Burgers vector and the angle between the crystal surface and the particle surface is small enough that the growth layer can bend as it climbs onto the particle.