High resolution TEM of dissociated dislocations in PbS

Abstract

The core structure of a/2 〈110〉 dislocations in PbS has been analysed by high resolution transmission electron microscopy. Dislocations on {100} and {110} slip planes are dissociated while those on {111} are perfect. The dissociation width d of 45° dislocations on {100} and edge dislocations on {110} has been estimated to about 5 and 2 Burgers vectors, respectively. The results support a correlation of d with the ionicity of the material as it is expected from elasticity theory: an increase of d on {100} and decrease of d on {110} and {111} with decreasing ionicity. Finally the slip behaviour of dislocations in ionic crystals is discussed in terms of dislocation dissociation and plastic anisotropy.