Silicon oxynitride gas barrier coatings on poly(ether sulfone) by plasma-enhanced chemical vapor deposition

Thin silicon oxynitride (SiOxNy) has been deposited for a gas barrier layer on the surface of poly(ether sulfone) film using plasma-enhanced chemical vapor deposition (PECVD) of a mixture of hexamethyldisiloxane (HMDSO) and ammonia. The chemical structure of the deposited layer varied from organic to inorganic structures depending on RF plasma input power applied to the reaction system. A silicon-based undercoat layer, which has an organic/inorganic hybrid structure, was used as an interfacial buffer layer between the organic PES and inorganic SiOxNy layer. With the help of the undercoat layer, the dense inorganic SiOxNy layer gave a superior oxygen barrier property of 0.2 cm3/m2 day at a critical coating thickness of ca. 20 nm. In a highly stressed SiOxNy film, the effect of the undercoat layer was remarkable in preventing crack formation during bending tests.