Effects of Deposition and UV Irradiation Conditions on Gas Permeability of Vacuum Evaporated SiOx Thin Films

SiOx thin films were vacuum deposited on a 25 μm thick PET substrate under various conditions. The effects of the chamber pressure, evaporating temperature, and deposited film thickness on the oxygen transmission rate (OTR) were investigated. The results were: (1) The lower the chamber pressure and the higher the evaporating temperature, the lower the OTR is except the chamber pressure of 1.3×10-2 Pa or lower. (2) Specimens having high OTR show high O/Si atomic ratio. It is suggested that deposited SiOx films of these specimens are porous or have a large surface area, so that a greater amount of SiOx is oxidized to SiO2. (3) UV irradiation decreased OTR from 0.056 to 0.009 pmol/m2•s•Pa with chamber pressure 6.6×10-2 Pa and evaporating temperature 1530 K. The reason suggested for this is activation and cleaning of the substrate and depositing surface.