Variable-energy positron studies of well-annealed single-crystal Cd samples from 35 to 450 K

Well-annealed Cd(001) and Cd(100) samples have been examined using a monoenergetic variable-energy positron beam (0.5 to 5.0 keV). The results are interpreted in the context of a one-dimensional-diffusion model which allows for annihilations as well as trapping at defects including thermally generated vacancies. The dependence on temperature of positron diffusion out of these samples was determined by the use of this model to interpret data taken between 35 and 450 K. The deduced positron diffusion length is in rough agreement with positron-acoustic-phonon scattering predictions between 35 and 170 K. No indication of positron localization in shallow traps is inferred from these results.