Real single crystals are not perfect or homogeneous; they contain various imperfections and inhomogeneities, such as growth sectors, vicinal sectors, growth banding, spatially distributed dislocations, and inclusions. Because these imperfections are induced either during or after growth, they provide us with informative records of growth processes. Crystals formed at higher growth rates may show lineage structure or split growth. Since we cannot observe the growth or post-growth processes directly in natural or synthetic crystals, these imperfections serve as an important information source, and they may be used to decode the growth process. In this chapter, we summarize and analyze how these imperfections and inhomogeneities are induced in single crystals.

Imperfections and inhomogeneities seen in single crystals

It would be foolish to assume that in real systems a constant growth rate is maintained throughout the whole crystal growth process, starting from nucleation through to the final stage. This is just as true in synthetic crystals grown under precisely controlled conditions as it is in natural crystallization, in which conditions are not controlled. The growth rates may vary for various reasons, resulting in fluctuations in impurity concentration and point defect density. Such fluctuations are recorded in single crystals in the form of “growth banding,” which arises due to fluctuating concentrations of point defects, impurities, and inclusions. Since growth rates are dependent on crystallographic direction, perfection and homogeneity will be different among “growth sectors” formed by the growth of respective faces.