A DOPPLER BROADENING POSITRON-ANNIHILATION TECHNIQUE FOR THE STUDY OFDEFECTS IN BULK SAMPLES

A Doppler broadening positron annihilation technique which allows for the study of near surface defects in bulk samples is described. The me thod is capable of observing changes in the homogeneous bulk defect co ncentration in a sample acid is also able to characterize spatially lo calized near-surface defects in bulk materials with a resolution of ab out 1 mm. The applicability of this method is demonstrated by measurem ents on a sample of polycrystalline aluminum into which defects have b een introduced by mechanical deformation. Isochronal annealing studies have been used to characterize the defect recovery in this material a nd are compared with results of conventional Doppler broadening measur ements.