Characterization of the He bubbles in Si probed by a positron annihilation spectroscopy

Maekawa, Masaki; Kawasuso, Atsuo

The helium bubble formed in silicon was observed by the positron annihilation method by the high-dose helium ion implantation. Helium ions were implanted to the silicon (irradiation dose: 210/cm at room temperature) with the energy of 50-200 keV. The peak intensities of annihilation rays (S parameter) and its annealing behaviors were measured. At as-implanted state, S parameter increased because of the implantation defects. After 300 C annealing, S parameter decreased. From the first principle calculation, positron trapping at the defect cluster of approximately 1 nm filled up with 36 helium atoms is suggested. This means that positrons are trapped to the irradiation defects filled up with the helium atoms. Positron annihilation method can detect the generation and disappearance process of the helium bubble by the ion implantation.