DEFECTS IN MEV SI-IMPLANTED SI PROBED WITH POSITRONS

Vacancy-type defects produced by implantation of MeV doses of Si ions (10(11)-10(15) atoms/cm2) at room temperature have been probed using depth-resolved positron annihilation spectroscopy. The defect (divacancy) concentration increases linearly with dose for low doses ( < 10(12) Si/cm2). In situ isochronal annealing was followed for oxygen-containing Si (10 ppm) and oxygen-''free'' Si implanted to doses (5 x 10(12) and 5 x 10(14) Si/cm2). Two main annealing stages were observed at the same temperatures in the studied samples in spite of significant differences in doses and oxygen content. In the first stage (approximately 200-degrees-C) a significant fraction of divacancies was observed to form large vacancy clusters. These clusters were removed in the second stage (approximately 675-degrees-C) after which the oxygen-free samples returned to pre-irradiation conditions, whereas oxygen-defect complexes were formed in the oxygen-containing samples.