Stoichiometric silicon nitride thin films for gas barrier, with applications to flexible and stretchable OLED encapsulation

This study reveals that the stoichiometricity of silicon nitride thin films (SiNx-TFs) significantly governs the packing density and water vapor transmission rate (WVTR), and it can be controlled by chemical reactions accompanied by the removal of oxygen impurities with a nitrogen neutral beam (N-NB). Here, oxygen contents of SiNx-TFs are reduced through the formation of volatile NOx, and their amount is dominated by the energy of the N-NB reflected from a negatively biased reflector (0 to −60 V). The single-layered stoichiometric SiNx-TFs with a thickness of 100 nm provides the WVTR of 6.2 × 10−6 g/(m2day), with a density and composition ratio of N/Si stoichiometry at 3.13 g/cm3 and 1.33, respectively. This optimized SiNx-TF encapsulated top-emission organic light-emitting diode has reliability under harsh condition (85 °C and 85% relative humidity) for 830 h or more.