Oxygen microclusters in Czochralski-grown Si probed by positron annihilation

Trapping of positrons by oxygen microclusters in Czochralski-grown Si was studied. Lifetime spectra of positrons were measured for Si specimens annealed in the temperature range between 450degC and 1000degC. Positrons were found to be trapped by oxygen microclusters, and the trapping rate of positrons into such defects increased with increasing annealing temperature. In order to investigate the clustering behaviors of oxygen atoms in more derail, vacancy-oxygen complexes, VnOm (n,m=1,2, ···), were introduced by 3MeV electron irradiation. The concentration of monovacancy-oxygen complexes VOm(m=2,3, ···) increased with increasing annealing temperature. These facts were attributed that the oxygen microclusters, Om, were introduced by annealing above 700degC. (author)