High-fluence implantation of iron into polyimide

Polyimide–Kapton (PI) foils were implanted with 40 keV Fe+ ions to a fluence of 0.25×1017, 0.75×1017 and 1.25×1017 cm−2 at ion current density of 4, 8 and 12 μA cm−2. The structure and composition of the modified PI were studied using Rutherford backscattering spectroscopy (RBS), proton-induced X-ray emission (PIXE) and transmission electron microscopy (TEM). A carbonaceous layer filled with up to 25 at.% of agglomerated metal particles is formed under the sample surface. Anomalous depth profiles of the implanted metal atoms, consisting of a strong near-surface peak and two weaker ones under the implanted layer, are observed. Possible mechanisms of the metal redistribution after implantation are discussed. The depth profiles of the implanted metals are not influenced by increasing ion current density. Under thermal annealing at 300 °C for 120 min, slow inward diffusion of Fe atoms is observed with diffusion coefficient 0.5–1×10−16 cm2 s−1.