X-RAY PHOTOELECTRON-SPECTROSCOPY INVESTIGATION OF INTERFACIAL INTERACTIONS IN THE CR BPDA-PDA AND TI BPDA-PDA SYSTEMS

Interfacial interactions of evaporated chromium and titanium with BPDA-PDA polyimide surfaces have been studied using x-ray photoelectron spectroscopy. The results reveal two stages in the metallization process. At low coverage, the behavior is dominated by the reaction of metal with the C=O function, as in the case of PMDA-ODA polyimide. The nitrogen atoms are slightly perturbed following the C=O attack. At relatively higher coverage, additional interfacial reactions occur, involving the formation of chromium and titanium carbides and nitrides. The results indicate clearly that the chemical interactions of Cr or Ti at BPDA-PDA and PMDA-ODA surfaces are quite similar. Thus, the diamine portions, PDA and ODA, can affect the adhesion strength, probably by modifying the polyimide chain conformation. In PMDA-ODA, the polyimide chain is flexible and can rotate around the ether oxygen, while in the BPDA-PDA the conjugation effect is more important and makes the macromolecules more rigid. This is most probably the way by which PDA and ODA segments can influence the adhesion performance of polyimide.