PECVD SiO2/Si3N4 double layers electrets on glass substrate

SiO₂/Si₃N₄ double layers electrets have been investigated for their long-term charge stability and compatibility to micro technology. This paper first reports SiO₂/Si₃N₄ double layers electrets both prepared by plasma enhanced chemical vapor deposition (PECVD) on glass substrates. Charging time, charging temperature and annealing process were studied for their influence on electrets properties. Different methods of treatment, such as hexamethyldisilazane (HMDS) coating, heat treatment at 250degC, 02 plasma treatment and their combinations, were employed to improve charge stability under high humidity conditions. The experimental results show that PECVD prepared SiO₂/Si₃N₄ double layers exhibit high performance in charge storage under different environmental conditions. The surface potential did not decay obviously at room temperatures during more than two months. The samples lose less than 20% of the surface potential at 250degC for more than 10 h. The surface potential could be kept more than 90% at 95% RH by heat treatment combined with HMDS process or O₂ plasma treatment.