Improvement of charge storage characteristics of silicon based polyvinylidene fluoride thin film through heat treatment and multiple layer stack

• Silicon based PVDF thin film electrets have been fabricated on Pt/SiO2/Si substrates.
• Heat treatment method influences surface morphology and compactness of PVDF thin film.
• Multiple layer stack exhibits better charge storage characteristics due to additional inter-layer interfaces.
• Optimally, RT-90 °C treated three layer stacks exhibit −548.6 V initial surface potential and 91.0% retain rate in 30 min.

To utilize polyvinylidene fluoride (PVDF) in novel integrated electrostatic devices, charge storage characteristics of PVDF thin film on wafer are analyzed and improved. Heat treatment method and layer thickness/stack are identified as two influencing factors. Among the four comparing heat treatment methods, the method of room temperature drying for 2 h followed by 90 °C baking for 3 h achieves PVDF films with better charge storage ability due to increased surface roughness and film compactness. Both initial surface potential and retain rate in 30 min increase as PVDF film thickness increases. Multiple layer stack exhibits better charge storage stability due to increased surface roughness and additional charge traps introduced by inter-layer interfaces. In this paper, optimal charge storage characteristics are obtained for three layer stack with 16 μm single layer thickness. Averagely, initial surface potential reaches −548.6 V and retain rate in 30 min reaches 91.0% @−600 V grid voltage & −6 kV needle voltage.