Improvement of the performance of the PECVD SiO2/Si3N4 double-layer electrets

In this paper, multiple approaches were attempted to improve the performance of PECVD SiO₂/Si₃N₄ double-layer electrets on glass, including different electrode structures, as well as various corona charging conditions. Both chargeability and charge stability of the PECVD SiO₂/Si₃N₄ double-layer electret at high temperature and high humidity were investigated. It is proven that samples with both lower and back electrodes has simpler process but exhibits similar chargeability and charge stability to those having lower electrode contact with ground directly by welding lead. High charging temperature can increase chargeability but has no effect on charge stability melioration. Long-term observation implies that if the electrets have to work outside properly, heat treatment will be necessary, although hermetic packaging is the best option. PECVD SiO₂/Si₃N₄ double-layer electrets can endure high temperature lower than 250°C and shows good charge stability under high humidity.