SiOxNy thin films were synthesized via ion-beam-assisted vapor deposition (IVD) where deposition of SiOx was irradiated by nitrogen ions. Firstly, reasonable-cost evaporation materials showing less splashing for the SiOx films were investigated by selecting appropriate sintering condition regimes of Si and SiO2 mixed powders. The SiOxNy thin films on a polyethylene terephtalate film substrate obtained via IVD showed a low oxygen transmission rate (OTR) of less than 1 cm(3)/m(2) day. Effective nitrogen ion irradiation energy per atom was 8 eV/at. or greater, which is consistent with regimes where densification of thin films is reported to occur. Higher N-2 partial pressure yielded a lower OTR and a higher nitrogen atomic ratio of the films obtained. It is suggested that the improvement in gas-barrier performance resulted from densification and chemical change of the films due to energy addition and nitrification produced by nitrogen ion-beam irradiation. 0 2006 American Vacuum Society.