The stacking faults and partial dislocations involved in structure transformations of ZnS crystals

Abstract

Morphological and structural studies of ZnS crystals grown from the vapour phase lead to the following conclusions: (a) A relatively small number of Shockley partials and associated stacking faults is sufficient to transform, by periodic slip process, the parent 2H structure to polytypes not having ‘1’ in their Zhdanov symbol, or to 3C. (b) The stacking faults are introduced by mechanical and thermal stresses, and by thermal agitation, (c) Shockley dislocation dipoles and multipoles take part in the structure transformations. A possible mechanism for the formation of dipoles of Shockley partials is proposed. It is shown that a ‘sandwiched’ stacking fault of the type ABACABA, together with its associated elementary dipole, should be a common fault in the hep and wurtzite structures, especially if the energy a of the intrinsic stacking fault is negative. From considerations of the total energy of the system: intrinsic stacking fault and Shockley partial, it is estimated that |a|<600 erg/cm2 in 2H ZnS.