Growth mechanism of cadmium iodide polytypes

Abstract

The mode of growth of CdI 2 crystals grown by vapour phase technique under stabilized growth conditions has been studied by taking their optical, X-ray and electron diffraction photographs. It has been found that in the initial stages of growth the CdI 2 molecules are deposited to give rise to a film consisting of very small crystallites. During subsequent growth considerable reorientation and coalescence take place to form a disordered layer structure. As the deposition proceeds further, the degree of disorder is reduced and the final deposit, in the form of a platelet, is found to be a regular single crystal exhibiting an ordered 4H structure. During this transition process there is some finite probability of forming a metastable structure, for a small period of growth, provided the growth conditions remain highly stabilized during that interval. Higher incidence of polytypism in the crystals grown either from solution or on substrate by vapour phase technique has also been discussed.