Improvement of oxygen barrier of polyethylene terepthalate film by plasma-source ion implantation of carbon

The surface of polyethylene terepthalate (PET) film has been successfully modified to amorphous carbon by plasma source ion implantation (PSII) as a means of improving the oxygen barrier characteristics of the PET film. The process was performed using high negative pulsed voltage in an radio frequency field with C2H2 gas. The amorphous carbon layer is found to consist primarily of graphite crystal with C-H, C-H2 and C-H3 components, and to reduce the oxygen transmission rate of the film by up to 100 times that of unmodified PET film at a thickness of only 70-300 nm. Raman spectra reveal that the amorphous carbon layer has diamond-like carbon characteristics, yet is soft compared to other diamond-like carbon films with hydrogen contents of >20 at. %. A stronger graphite character in the x-ray photoelectron spectroscopy spectra is found to represent the fineness of the carbon structure and correlate well with the improvement of oxygen barrier characteristics