Hydrogenated amorphous carbon film coating of PET bottles for gas diffusion barriers

The addition of a gas-impermeable coating on the inside wall of a standard polyethylene terephthalate (PET) bottle has long been considered as a way to improve the packaging for beer, juice and carbonated soft drinks. We have developed a plasma-assisted deposition process suitable for the deposition of 100 nm thick, transparent, hydrogenated amorphous carbon (a-C:H) films on PET surfaces. The Sidel plasma technology uses an acetylene gas precursor and a microwave plasma, which allows us to obtain a high deposition rate of 60 nm/s necessary for industrial process flows. The a-C:H films provide a 50-fold reduction of the permeation rates of O2. The composition, optical, structural and defect properties of the a-C:H films were characterized by Rutherford Back Scattering (RBS), Elastic Recoil Detection Analysis (ERDA), X-ray Photoelectron Spectroscopy (XPS), optical spectroscopy, Raman and Electron Paramagnetic Resonance (EPR).