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 d epth-resolved positron annihilation spectroscopy. The defect (divacanc y) concentration increases linearly with dose for low doses ( < 10(12) Si/cm2). In situ isochronal annealing was followed for oxygen-contain ing 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 diff erences 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 sampl es returned to pre-irradiation conditions, whereas oxygen-defect compl exes were formed in the oxygen-containing samples.