An alternative interpretation of positron annihilation in dislocations

The interaction between positrons and dislocations is considered from a new point of view, which leads to a new interpretation of positron results obtained for metal samples containing dislocations. The positron binding energy in a perfect dislocation line is assumed to be small (approximately equal to 0.1 eV). The observed changes in the positron annihilation parameters due to the presence of dislocations then originate from annihilation in point-like defects (e.g. jogs) associated with the dislocation line. The positron-dislocation line trapping rate due to phonon emission is calculated for various binding energies and temperatures and is found to be unexpectedly large. It is shown that this interpretation predicts strong temperature dependences for the positron trapping rate in annealed samples at temperatures below 300 k due to positron detrapping. (author)