Stacking faults in sphalerite and formation of ZnO in TEM

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Zinc sulfide (ZnS) has two polymorphs (or polytypes), sphalerite and wurzite. The structure of sphalerite is face-centered cubic (fcc) packing of sulfur atoms, whereas that of wurzite is hexagonal close packing (hcp). However, energy difference of the two structures is very small, resulting in the mixture of the two structures in a crystal, forming disorder of stacking along the <111> direction of sphalerite. The movie shows HRTEM imaging of synthetic sphalerite particles along <110>, showing dense stacking faults or microtwins in them. Moreover, around the end of the movie nano-particulates with different lattice-fringe spacing are nucleated on the surface of the crystal. They are ZnO, formed by dissociation of ZnS by electron radiation and reaction of dissociated Zn with O2 in the residual gas in vacuum.
See Kogure and Bando (1998) for the detail. TEM: Hitachi HF-2000 at 200 kV.

Kogure, T. and Y. Bando: "Formation of ZnO nanocrystallites on ZnS surface by electron beam radiation", J. Electron Microsc., 47(2) (1998) 135-141