Distribution of stacking faults in zinc sulphide crystals grown from the vapour

Abstract

A calculation of the degree of disorder and the interaction energy of all known ZnS polytopes, on the basis of Schneer's theory, shows that they may be regarded as intermediate states in a gradual 3C-2H transition occurring with the rise in temperature. Experimental investigation of the dependence of structure and the distribution of stacking faults on the conditions of growth from the vapour has yielded interesting results. Crystals grown in vacuum were found to be needle-shaped with a variable random disorder due to stacking faults with little tendency to form polytopes. Structures predominantly cubic were found to grow even at a temperature of 1200°C, while a significant proportion of the 2H structure was present in crystals formed at 575°C.Crystals grown from the vapour in an inert atmosphere were found to be both needles and platelets, with a marked tendency towards a periodic occurrence of stacking faults. The tendency towards polytypism was found to be maximum in platelet crystals which emit blue light under X-ray irradiation. It is suggested that the occurrence of polytypism is related to the influence of an orderly arrangement of stacking faults on the electron energy.