Positron annihilation spectroscopy was used, together with anodic oxidation and etching techniques, to profile the distribution of open-volume defects beyond the range of 120keV Ge ions which were implanted into (100) samples to a dose of 1014/cm2. For a time-averaged dose-rate of 0.02μA/cm2, and an incident angle of 7º, open-volume defects were found to exist in concentrations exceeding 1016/cm3 at depths of up to 600nm. The peak of the depth distribution of implanted Ge ions was 76nm; as measured using secondary ion mass spectroscopy. An increase in the depth of the defects, which was observed when the implant was intentionally channelled along the <100> axis, was thought to be simply related to a corresponding increase in the projected range to 79nm. When the time-averaged current was increased by a factor of 10, defects persisted at concentrations in excess of 1017/cm3 beyond 1μ and the projected range increased to 101nm. This extended tail was attributed mainly to increased defect diffusion.

Open-volume defect tails in Ge-implanted Si A.P.Knights, A.Nejim, P.G.Coleman, H.Kheyrandish, S.Romani: Applied Physics Letters, 1998, 73[10], 1373-5