Ion irradiation induced impurity redistribution in Pt/C multilayers

Ion irradiation induced modifications of a periodic Pt/C multilayer system containing Fe impurity have been analyzed by X-ray techniques suitable for exploring nanometer depth scales with sub-nanometer depth resolution. The multilayer stack with 15 Pt/C layer pairs (period 4.23 nm, total thickness 63.45 nm) was fabricated on a glass substrate. A 2 MeV Au2þ ion beam was rastered on the sample to obtain uniformly irradiated strips with fluences from 1 10 to 1 10 ions/cm. These strips were analyzed with X-ray standing wave and X-ray reflectivity experiments. Ion induced atomic displacements across multilayer interfaces are known [Appl. Phys. Lett. 79 (2001) 467]. Here additionally we identify irradiation induced redistribution of Fe impurity atoms, which cannot be explained simply by atomic displacements due to ion–atom collision. With increasing ion fluences more Fe atoms migrate from Cto Pt-layers. This behaviour has been explained in terms of radiation induced enhanced diffusion and Fe–Pt and Fe–C phase diagrams. 2003 Published by Elsevier B.V. PACS: 61.80; 68.65.A; 68.49.U