Nano-fabrication of wavy silicon dioxide films for ultra-stretchable encapsulation films

Abstract

Recently, organic electronic devices are widely studied for flexible applications. Organic components in device are vulnerable to external environment such as high temperature and humidity. To ensure chemical stability and long-term operation, organic electronic devices require encapsulation layer with low water vapor transmittance rate. Encapsulation materials of commercialized rigid OLEDs are rigid glass and epoxy resin, which are not suitable for flexible devices requiring high flexibility. TFE (thin-film encapsulation) technique has been studied for flexible device encapsulation. Amorphous materials are selected for TFE because they are dense and transparent and do not have fast diffusion path like grain boundary. Among these materials, a thermally-grown silicon dioxide, oxidized from single crystal silicon substrate at high temperature, has ultra-low water vapor transmittance rate due to high density without pinholes and defects. However, the thermally-grown silicon dioxide thin films have a low elastic limit (<1%) and show brittle fracture alike typical amorphous materials. For that reasons, it is necessary to improve the mechanical properties of the thermally-grown silicon dioxide thin film for thin-film encapsulation. In this study, we tried to improve the stretchability by applying the wavy structure to the TFE, and developed the wave structure texturing of single crystal silicon substrate by using various etching process. And then we fabricated a high-quality wavy structure amorphous silicon dioxide TFE by the thermal oxidation of the wavy substrate. In addition, we carried out tensile test and finite element analysis on the wavy and flat thin films to analyze the stretchability. And then, we analyze the correlation between the stretchability and wave structure of the wavy thin film.