Range distribution of low-energy nitrogen ions in metals

The range distributions of ${\mathrm{N}}_2^{+}$ in copper and silver have been determined for energies up to 5 keV. The distributions show a sharp peak at the surface along with a deeper shoulder or secondary peak and a long tail into the sample, contrary to theory which predicts only a near-Gaussian distribution in the sample. Careful examination indicates that neither the possible physical or chemical properties alteration by ion bombardment nor experimental error is the cause of the enrichment of nitrogen near the surface and therefore confirms the presence of this peak as part of the distributions. The energy dependence and the depth of the secondary peak, however, are in reasonable agreement with those predicted by available theories for the projected range distribution of implanted species.