OCCURRENCE OF GLISSILE SHOCKLEY LOOPS IN FIELD-ION SPECIMENS OF IRIDIUM

The paper describes observations of faulted loops with Burgers vector of the α/6⟨112⟩ type in iridium field-ion specimens. The densities observed in some specimens are as high as 1018 loops per cm3. The occurrence of these loops is related to fracture of the specimens and specimen asymmetry. It is suggested that the high shear stresses operating on a field-ion specimen during imaging and evaporation homogeneously nucleate glissile Shockley loops. In some cases the intersection of these loops leads to a crack nucleus and then to fracture. The presence of some image streaks in asymmetric specimens is shown to be related to the presence of faults, produced by shear, intersecting the surface. © 1968 Taylor & Francis Group, LLC.