Structural and chemical effects of low energy ion bombardment of PMDA-ODA surfaces

Abstract

The effects of ion irradiation on polyimide surfaces have been studied using x-ray photoemission techniques. Ion bombardment with energies in the range 0.5–2.0 keV and doses between 8×1013 and 1×1015 ions/cm2 were carried out in situ in the x-ray photoelectron spectrometer and the chemistry of the modified surface was monitored using core level spectral changes. At low doses and energies, carbonyl groups were preferentially sputtered keeping the rest of the monomer intact. Loss of nitrogen was insignificant compared to losses of carbon and oxygen. At higher energies and doses, the polymer undergoes extensive bond scission, restructuring of various functional groups and species, together with radical and anion formation. High resolution spectra indicated a binding energy scale shift to a lower value, which increased with ion energy and dose, and which was related to the creation of a surface negative charge. The effects of exposure to moisture in the ambient on the surface charge, on the surface structure, and on the surface chemistry was studied.