Detection limits of heavy elements such as Fe or Cu near the surface of silicon was investigated by PIXE using slow heavy ions (<90 keV/amu). Fe atoms were implanted in silicon at 343 keV energy to a dose of 1 × 10 13 −1 × 10 15 Fe/cm 2 and Cu was introduced in silicon to the dose of 5 × 10 14 Cu/cm 2 . PIXE spectra were obtained by 5.2 MeV 58 Ni 3+ and 74 Ge 3+ beams in order to enhance the yield of Fe or Cu K X-ray by MO process. The results were compared with those obtained by a 2 MeV proton beam. In the case of slow heavy ion impact, bremsstahlung background above 5 keV was much lower than that of protons. Moreover, Fe Kα X-ray production in Fe implanted silicon was enhanced by using the 5.2 MeV 58 Ni 3+ beam. As a result, the detection limit of Fe in silicon was successfully improved. However, Cu Kα X-ray production in Cu contaminated silicon was not so enhanced by using the 5.2 MeV 74 Ge 3+ beam and the detection limit could not be improved.