Low-temperature ion-beam mixing of platinum markers in iron

Thin platinum markers approx.=10 A thick buried 400 A below the surface of approx.= 2,400 A thick iron films have been ion-beam-mixed by 150 keV argon ions. Using RBS analysis with 1.0 MeV He2+, the mixing was characterized by a broadening of the markers. The mixing was measured as a function of ion dose, target temperature, and oxygen-impurity concentration. The oxygen impurities reduced the mixing. A step in the mixing as a function of temperature was observed at 25 K, i.e., below stage Isub(D), in iron. Furthermore, deviations from a square-root dependence of the mixing on the argon fluence were observed in several cases. A model based on dynamical-cascade mixing cannot explain these observations. We suggest that interstitial diffusion plays a role in the mixing. (orig.)