Structure of dislocations in germanium

Two-beam tilt {111} lattice images were made of dislocations in germanium crystals deformed by compression or torsion. {110} slices were cut out normal to the main glide planes and chemically thinned. The displacement field was measured around a 60° dislocation running normally through a foil cut from a twisted crystal, which gave a lattice image with perfect symmetry about the terminating fringe. After suitable correction, the measured width on the Peierls-Nabarro model was 5.2 Å, about a factor of 2.5 greater than expected from a theory by Labusch. The measurement involved the assumption that a direct correspondence exists between fringe and lattice plane positions in the special case studied.