Morphological Stability of a Linear Step in the Presence of a Mobile Adsorbed Impurity
As a growth front moves, concentration gradients form for an impurity (owing to its repulsion by the crystal) and the main substance (owing to its absorption by the crystal during growth from solution). These concentration gradients can cause the initially planar phase boundary to become unstable [1–3]. The random sinusoidal profile with time becomes more regular. The surface acquires a cellular (or macroscopically stepped ) structure. Movement of a linear step produces an analogous situation. Even if the medium (liquid or gaseous solution) is mixed well and is completely homogeneous, lateral concentration gradients due to surface diffusion of the main substance and impurities arise near the step. These lateral surface-concentration gradients can destabilize the linear step and produce a two-dimensional cellular structure.
KeywordsCrystallization Migration Anisotropy Supersaturation Stopper
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