Defects in high energy ion implanted silicon have been investigated, especially in the depth range around half of the projected ion range RP/2 after annealing at temperatures between 700 and 1000 °C. Preferable trapping of metals just in this depth range proves the existence of defects there. No vacancy-like defects could be detected by variable energy positron annihilation spectroscopy after annealing at temperatures T≫800 °C. Instead, interstitial-type defects were observed in the RP/2 region using cross section transmission electron microscopy of a specimen prepared under special conditions. The results indicate the presence of small interstitial agglomerates at RP/2 which remain after high temperature annealing. © 1999 American Institute of Physics.