Variable energy positron defect profiling has revealed the sub‐surface vacancy profile in Cz Si(100) implanted to a dose of 2×1014cm−2with 120 keV fluorine ions. We demonstrate the presence of vacancies at ppm concentrations at depths exceeding 1.5 &mgr;m, many times the depth at which implantation damage is expected to occur. The vacancy profile deduced was verified by removing layers of known thickness from the surface of the sample by chemical etching and repeating the defect profiling process. In the fitting procedure, the use of a Monte Carlo deduced positron implantation profile isrequired. The annealing behavior of the defects shows that the vacancies caused by the implantation process consist of two components. The deep vacancies are found to be relatively easily removed by a moderate temperature anneal, in contrast to those vacancies nearer to the surface. The former component is suggested to be the more mobile and thus may diffuse to the depths at which it is observed.