Positron characteristics, at temperatures ranging from 10 to 300K, were investigated in monocrystals that had been deformed under various conditions. Positive temperature dependences were found for the annihilation parameters. The average rate of increase of S as a function of temperature appeared to be controlled by the dislocation density and the vacancy concentration which was introduced by deformation. A positron trapping model was proposed which assumed a trapping at dislocations which decreased exponentially with temperature, plus thermally activated de-trapping from dislocations and temperature-independent trapping at deep traps. This model predicted the occurrence of a temperature-dependent competing trapping that determined the temperature dependences of the annihilation parameters. The positron binding energy for dislocation lines, their positron trapping coefficient, the dislocation density and the rate of trapping at deep traps could be determined by fitting the observed temperature dependences to this competing-trap model. This method permitted quantitative investigation of the evolution of the defect structure of metals during recovery.

A Model for Interpreting the Positron Annihilation Characteristics of Deformed Metals: Application to Vanadium T.Leguey, R.Pareja: Journal of Physics - Condensed Matter, 1998, 10[11], 2559-78