Micro-Raman study of the carbonization of polyimide induced by swift heavy ion irradiations

• Published in: Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms Beam interactions with materials and atoms, 2002-08, Vol.194 (2), p.132-140
• Main Authors: Costantini, J.-M., Couvreur, F., Salvetat, J.-P., Bouffard, S.
• Format: Article
• Language: English
• Subjects: Electronic excitations; Heavy-ion irradiations; Polyimide; Raman spectroscopy
• ISSN: 0168-583X; 1872-9584
• DOI: 10.1016/S0168-583X(02)00669-9

We have done an extensive study of damage of polyimide (Kapton-H) thin films by heavy ion irradiations in the 1 MeV amu −1 energy range. We found that the irradiation-induced insulator–conductor transition proceeds through four stages on the basis of the progressive formation of a 3D graphite-like structure when track overlaps increase. All bulk dc conductivity and paramagnetic center volume density data were rescaled on a plot versus fluence ( φt) times electronic stopping power ( S e) squared i.e. φtS e 2. Visible micro-Raman spectra were recorded in order to monitor the ion-induced modifications. It is seen that the spectral features of the pristine polymer progressively disappear during stages I and II, and that only two broad peaks at around 1360 and 1580 cm −1, corresponding respectively to the well-known D and G bands of disordered graphitic materials, remain in stages III and IV regardless of the ion. We address the evolution of the polymer material according to the four stages of the transition versus φtS e 2.