Oxygen in silicon: A positron annihilation investigation

摘要

Positron lifetime and Doppler broadening investigations of oxygen in silicon (Cz silicon) have been performed. It was found that positrons may be trapped by defects yielding a positron lifetime of only 100 ps and a momentum distribution of the annihilation quanta which is wider than that for defect‐free silicon. This unequivocally shows that clusters of oxygen constitute positron traps. The trapping process was found to be thermally activated in the 25–300 K range. Isochronal and isothermal annealing showed that the clusters alternate during growth between having an interstitial character and a vacancy character. At 450 and 500 °C, growth of oxygen clusters takes place with an activation energy of 1.5 eV, while at 650 and 714 °C, these clusters disappear with an activation energy of 1.1 eV. At 714 and 790 °C, growth of new clusters takes place with an activation energy of 2.6 eV.