Variable-energy positron annihilation spectroscopy was used to study the behavior of O-related defects that were produced by the implantation of 180keV O ions to a dose of 2 x 1015/cm2. In the first annealing stage of these defects (at about 600C), multi-vacancy O complexes that were introduced by room-temperature bombardment were transformed into multi-vacancy multi-O ones in the implanted region. At temperatures above 800C, new trapping sites were created where positrons were annihilated by electrons with a high momentum within a limited region of the wafer. These defects were suggested to be O clusters that involved several tens of O atoms. The results clearly showed that positrons were a sensitive probe for the detection of O-related defects which were not observable by using electron microscopy.

M.Fujinami: Physical Review B, 1996, 53[19], 13047-50