We investigated the characterization of silicon oxide (SiO2) films on polyethersulfone (PES) substrates by plasma-enhanced chemical vapor deposition for transparent barrier applications. The film properties, such as deposition rate, etch rate, roughness, and water vapor transmission rate (WVTR), were found to increase as the plasma power increased from 10 to 120 W. As the pressure of chamber increases from 75 to 375 mbar, the deposition rate, etch rate, and roughness increase while the WVTR decreases. Under optimum conditions, the WVTR for PES can be reduced from a level of 50 g/m(2)/day (bare substrate) to 0.31 g/m(2)/day after application of a 100-nm-thick SiO2 coating at 150 degreesC. A more efficient way to improve permeation of PES was carried out by using a double-side coating of a 100-nm-thick SiO2 film. It was found that the WVTR can be reduced to a level of 0.1 g/m(2)/day The double-side coating on PES could contribute to the lower stress of oxide film, which greatly improves the WVTR data. These results indicate that the SiO2/PES barrier coatings have high potential for flexible organic light-emitting diode (OLED) applications. (C) 2004 Elsevier B.V. All rights reserved.