Dislocation nets in bismuth and antimony tellurides

The electron microscopic examination of thin foils of bismuth and antimony telluride, prepared by repeated cleavage, reveals the presence extended dislocation patterns. Since the c-plane is simultaneously glide and cleavage plane, the dislocation arrangements are preferentially situated in the plane of observation. This is a considerable advantage if one wishes study the configurations due to glide, since one might hope that the typical thin foil behaviour would not apply to the glide planes parallel to the foil. Sets of concontric dislocation lines are often observed, but they invariably originate in soma invisible source, outside the crystal. In the c-plane very extended nets are often observed. The multiplication of dislocations and the resulting formation of networks, as well as the elimination of dislocations are observed whilst in progress. The latter phenomenon is due to a combination of glide and climb. Some contrast effects are also mentioned.