A strong gettering effect appears after high-energy Si self-implantation and subsequent annealing in two zones at the projected range of the silicon ions (Rp) and in a region at about Rp/2. The defects responsible for the impurity gettering at Rp/2 were studied by means of positron annihilation. It was found that diffusing Cu impurities were captured by small vacancy agglomerates. Monoenergetic positron beams with improved depth resolution were used to characterize the defects. Excellent depth r... »