Microscopic structure studies of ZnS crystals using synchrotron radiation

Laue diffraction spots are exact geometrical projections of the sample, if synchrotron radiation is the X-ray source. Using this principle, inhomogeneous ZnS crystals grown from the vapour phase were studied. The crystals consisted of uniform regions, having various widths; even the narrowest (≈ 1 μmm| resolvable ones had a well-defined crystal structure : cubic, 2H or polytypic. Heating up to 250°C caused, in one case, some structural transformations apparently towards less hexagonal polytypes, but without changing the boundaries of the uniform regions. The results are in full accord with a model of polytype formation based on expansion of stacking faults governed by a screw dislocation (Alexander, Kalman, Mardix and Steinberger 1970). The applicability of synchrotron radia tion Laue micrography to other non-uniform systems is also discussed.