Influence of low energy argon plasma treatment on the moisture barrier performance of hot wire-CVD grown SiN_x multilayers

The reliability and stability are key issues for the commercial utilization of organic photovoltaic devices based on flexible polymer substrates. To increase the shelf-lifetime of these devices, transparent moisture barriers of silicon nitride (SiN_x) films are deposited at low temperature by hot wire CVD (HW-CVD) process. Instead of the conventional route based on organic/inorganic hybrid structures, this work defines a new route consisting in depositing multilayer stacks of SiN_x thin films, each single layer being treated by argon plasma. The plasma treatment allows creating smoother surface and surface atom rearrangement. We define a critical thickness of the single layer film and focus our attention on the effect of increasing the number of SiN_x single-layers on the barrier properties. A water vapor transmission rate (WVTR) of 2×10^%4 g/(m²·day) is reported for SiN_x multilayer stack and a physical interpretation of the plasma treatment effect is given.