Dendritic growth of PbI₂ single crystals and study of their polytypism and growth features

Dendritic single crystals of highly purified lead iodide were grown from the vapour phase in vacuum. XRD was employed to characterize them and to study their polytypism and related behaviour. Most crystals were found to consist of the common polytype 12R_O and 12R_R. Streaking of the reflections was not seen in the X-ray photographs, but nearly 12% of the photographs showed arcing of the reflections. The surface microtopographic study of the basal (0001) faces of the crystals revealed typical dendritic growth features. Layer-by-layer growth by two-dimensional nucleation was frequently observed, while spiral growth was not observed at all.