ESR STUDY OF THE INSULATOR-CONDUCTOR TRANSITION IN POLYIMIDE KAPTON INDUCED BY SWIFT HEAVY-ION IRRADIATIONS

Kapton-H thin films have been irradiated with heavy ions in the MeV/u range, in the electronic stopping power (Se) regime. Effective ion tra ck radii are extrapolated from spin density measurements and are consi stent with simulations of the radial distribution of the energy densit y deposited by secondary electrons. This yields an apparent quadratic dependence of the data versus Se. We postulate that the paramagnetic d efects are dangling bonds on aromatic condensed structures, and that c onductivity appears by overlap of these structures. The final product is a highly amorphous carbonaceous substance with a conductivity (10(4 ) Ohm(1).m(-1)) and a spin density (5 x 10(19) g(-1)) near that of ion implanted or pyrolysed Kapton.