LATENT TRACK EFFECTS OF SWIFT ARGON IONS IN POLYIMIDE

A stack of polyimide (PI) thin foils was irradiated with 900 (MeVAr15)-Ar-40 ions up to a fluence of 8 x 10(11) ions/cm(2). Subsequently, t he electrical conductivity and UV-VIS absorption spectra of specimens were measured for the selected foils from the irradiated stack. Two we ll defined characteristic absorption peaks at wavelengths 482 and 501 nm appeared after irradiation and their absorption peak intensities pr ogressively increased with increasing electronic energy loss in the su bstrate. Over a range of deposited electronic energy density from 8 to 23 eV/nm(3), the depth profile of the chemical yields closely pursued the electronic energy transfer profile. The integrated optical absorp tion bands at 482 and 501 nm were used to evaluate the normalized dama ge fraction, the damage production cross-section and the track radii i n the irradiated PI matrix as a function of deposited electronic energ y density. The measured enhanced electrical conductivity substantiated by the optical band gap values was attributed to the formation of con densed polycyclic aromatic ring compounds and clusters with greater de gree of conjugation in the multiple overlapping ion track in the PI ma trix. The critical energy loss rate (track etch threshold) for Ar-40 i on in PI was obtained from the optical absorbance and electrical condu ctivity measurements. (C) 1998 Elsevier Science B.V.