An X-ray diffraction study of faulting in single crystals of cubic ZnS grown from the vapour phase

Abstract

An X-ray diffraction study is made in order to determine the nature of stacking faults present in vapour-grown cubic ZnS crystals, as well as in cubic crystals obtained by solid-state transformation from the 2H phase by thermal annealing. For this the point intensity distribution along the 10.L reciprocal lattice row of both kinds of disordered 3C crystals was recorded on a single-crystal diffractometer. The observed intensity profiles are found to be asymmetrically broadened and do not show any peak shifts, indicating that stacking faults present in both as-grown and annealed crystals are predominantly twin faults distributed randomly. The experimentally obtained intensity profiles are compared with those calculated theoretically for a random distribution of twin faults. The experimental results indicate (i) that the disordered 3C structures result by solid-state transformation of the 2H phase during the cooling of the growth furnace (ii) that they contain a random distribution of twin or growth faults and (iii) that the 2H-3C transformation in ZnS occurs by the non-random nucleation of deformation faults, occurring preferentially at two layer separations.