Highly-stretchable and water impermeable thermally-grown silicon dioxide thin film with wavy structures

Abstract

Organic components in organic electronic 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 of commercialized 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 materials because they are dense and transparent and do not have fast diffusion paths like grain boundary. 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 TFE. In this study, we tried to improve the stretchability by applying the wavy structure to thermallygrown silicon dioxide and developed the wavy structure texturing of single crystal silicon substrate by using photo-lithography and various etching process. we fabricated a highly-stretchable wavy thermally-grown silicon dioxide TFE by oxidizing wavy textured crystalline silicon substrate. Also, we carried out tensile test and finite element analysis on the wavy and flat thermally-grown silicon dioxide TFE to analyze the stretchability. And then, we discussed about the correlation between the improvement of stretchability and wavy structure.