The Direct Identification of Stacking Sequences in ZnS Crystal by High Resolution Electron Microscopy

An infinite variety of stacking sequences between that of the ideal 2H and 3C end-member structure is possible. More than 150 ordered ZnS phase (polytypes) have been reported, the majority of them in synthetic ZnS. Some degree of stacking disorder is very common, and completely disordered structures have also been reported. No direct identification of stacking sequence has been published, although Hashimoto reported structure image of synthetic ZnS. High resolution lattice imaging at the 2.5Å level with tilted-beam illumination established that essentially one-dimensional information about individual stacking sequences was directly obtainable. It has been possible to identify directly the detailed stacking sequence in longer period polytypes and around the vicinity of stacking faults, without recourse to any confirmatory calculations based on postulated trial structures. We have applied this method to the direct identification of stacking sequences in disordered ZnS crystals.