Effects of defects in SiO2 thin films prepared on polyethylene terephthalate by high-temperature e-beam deposition

In this study, we characterized silicon oxide (SiO2) thin film prepared on polyethylene terephthalate (PET) substrates by electron-beam (e-beam) deposition for transparent barrier application. As the chamber temperature is increased from 30 to 110 degrees C, the roughness increases while water vapor transmission rate (WVTR) decreases. Under these conditions, WVTR of PET can be reduced from a level of 0.57 g/m(2)/day (bare subtrate) to 0.05 g/m(2)/day after application of a 200-nm-thick SiO2 coating at 110 degrees C. A more efficient way to improve permeation of PET was carried out by using a double sided coating of a 5-mu m-thick parylene film. It was found that WVTR for PET substrates can be reduced to a level of -0.2 g/m(2)/day. The double-sided parylene coating on PET could contribute in lowering the stress of oxide film, which greatly improves the WVTR data. These results indicate that the SiO2/parylene/PET barrier coatings have a high potential for flexible organic light-emitting diode (OLED) applications.