INFRARED-ANALYSIS OF THE IRRADIATION EFFECTS IN AROMATIC POLYIMIDE FILMS

A Fourier transform infrared (FTIR) spectroscopic investigation of the ion-beam-induced chemical and structural modification in polyimide (PI) films is presented. Our experimental considerations provide a foundation for a quantitative evaluation of the infrared (IR) results for this thermally stable polymer on the deterioration of chemical bonding with irradiation fluence. It is found that chemical structure in PI is subjected to a severe alteration within the dose range from 1 x 10(14) to 1 x 10(15) B+/cm2. The radical structure modification is completed only as irradiation reaches 1 x 10(16) B+/cm2, at which point one may find that there exists a resemblance in profile shape between the IR spectrum of the high-dose irradiated PI film and the one-phonon states density (DOS) of amorphous graphite. This suggests that a structure similar to amorphous graphitic carbon films will be formed in the ion-beam-modified PI film when dose comes to a certain threshold. This ''graphitization'' process under ion bombardment is also supported by the experimental results from ultraviolet (UV)-visible spectroscopic study.