Polyimide modified by irradiation with C+ and N+ ion beams

Structural and compositional changes of polyimide induced by irradiation with 100 keV C+ and N+ ions to the fluences of 3×1015-1×1017 cm-2 were studied with the aim of clarifying whether implanted C, contrary to chemically inert N atoms, takes part in chemical reactions initiated by the irradiation. Electrical conductivity of the irradiated specimen was examined using a two-point technique, the depth concentration profiles of selected elements were determined by means of Rutherford back-scattering (RBS) and the chemical and structural changes were determined using FTIR and UVVIS spectroscopies. Contrary to N atoms, a part of the implanted C atoms was found to be incorporated in the radiation damaged surface layer of the polymer and in this way it contributed to an increased concentration of the conjugated double bonds and to an increase of electrical conductivity. Irradiation with both ion species leads to polymer deoxidation (decarbonylation), which manifests itself by degradation of imide groups accompanied by simultaneous production of amide groups. As for surface morphology, the irradiation with both ion species at fluences below 1×1016 cm-2 results in a significant increase of the polymer surface roughness. The PI surface roughness created by the ion irradiation is nearly the same for C+ and N+ ions.