Improving the oxygen barrier properties of PET polymer by radio frequency plasma-polymerized SiOxNy thin film

Plasma-polymerized silicon oxynitride (SiOxNy) oxygen barrier thin film was deposited on polyethylene terephthalate substrate by plasma enhanced chemical vapor deposition at low temperature. The deposition reactor utilizes capacitively coupled plasma operating at radio frequency (13.56 MHz). Nitrogen incorporation during the polymerization leads to a SiOxNy dense film with low defects which assists to improve the oxygen barrier properties. The gas mixture of tetraethyl orthosilicate as organosilicon precursor with oxygen and nitrogen gases was used to deposit the transparent polymerized SiOxNy thin films. The effects of nitrogen flow rate on deposition rate, refractive index, surface morphology, surface wettability, chemical structure and binding composition and oxygen permeability of the barrier films were investigated. Moreover, the plasma parameters were monitored by optical emission spectroscopy. SiOxNy oxygen barrier films showed 89-91% transparency. Under the optimal deposition conditions the minimum oxygen permeability of 0.08cm(3)/cm(2)day bar was obtained.