The recoil implantation yield of copper and gold into silicon substrates under14N+,31P+, and40Ar+ion bombardment has been studied using the backscattering method. The dependence of the yield on the incidence energy follows Sigmund's prediction, excepted at higher energies where enhanced diffusion has been observed. Furthermore, measurements of depth distribution of recoiled atoms have been performed using the neutron activation analysis. The profiles show a maximum at a penetration depth of about 60 Å which is explained by a low-energy cross-section in the energy-depth conversion.