Oxygen-related defects in Si studied by variable-energy positron annihilation spectroscopy

Variable-energy positron annihilation spectroscopy has been applied to study the behavior of oxygen-related defects in Si caused by implantation of 180-keV oxygen ions (2x10(15)/cm(2)). In the first annealing stages of these defects (similar to 600 degrees C), multivacancy-oxygen complexes induced by room temperature irradiation are transformed into multivacancy-multioxygen ones in the ion-implanted region. Above 800 degrees C, new trapping sites, where positrons are annihilated by electrons with high momentum, are created in a limited area inside the Si wafer. These defects are attributed to oxygen clusters involving several tens of oxygen atoms. The study clearly proves that positrons are a sensitive probe to detect oxygen-related defects, which are not observable by electron microscopy.