Impurity-defect interaction in ion-implanted supersaturated Au-Fe alloys

The annealing behavior of Au-implanted Fe single crystals has been studied by means of the channeling and backscattering technique. Room-temperature implants of (3–5)×${10}^{16}$ Au ions/${\mathrm{cm}}^2$ at 700 keV resulted in metastable supersaturated Au-Fe alloys. Large changes of the Au depth distributions and the lattice-site location were found after isothermal anneal sequences. Three well-distinguished annealing stages were observed: stage 1, 350–450 °C—precipitation of Au; stage 2, 500–650 °C—migration of Au towards the surface; and stage 3, over 650 °C—back-diffusion of Au into the bulk. The analysis of the time dependence of these processes leads to the conclusions that migration of vacancy-impurity complexes with an activation energy $E_a$=1 eV is the dominant mechanism in stages 1 and 2, whereas in stage 3 the solubility-limited diffusion with $E_a$=2.9 eV takes place.