Using RHEED to study polytypism

Abstract

Up to now, relatively few papers have dealt with electron beam investigations of polytypic substances. Recent work in Sic (Gauthier, 1978) pointed out the general interest in the use of reflection high energy electron diffraction (RHEED) for examining well-ordered long-period mod8ications. The main results are summarized here, showing what information can be obtained from RHEED patterns for the determination of polytype structures and hence possible explanations of growth mechanisms. In the same way, other materials have now been examined by the same technique and some results from zinc sulphide crystals are presented as an illustration. The mixtures of different ZnS modifications are complex; moreover, polytype disorder exists commonly in that substance. Such a situation vindicates the use of other techniques, particularly high resolution electron microscopy.