Humidity dependence of the electrical properties of fluorinated polyimide thin film prepared by spin coating and vapor deposition polymerization method

摘要

Electrical conduction and electrical capacitance in fluorinated polyimide (PI-F) thin film capacitor prepared by spin coating and vapor deposition polymerization (VDP) have been investigated in a thermostatic vessel in which relative humidity (%RH) was controlled. In the case of spin coated PI-F, the electrical capacitance changed almost linearly over humidity range of 30-80%RH. Hysteresis of the capacitance change became very small and response became much faster when Au electrode was used instead of Al. Conductive current increased exponentially with the %RH and the temperature. In the case of PI-F prepared by VDP there was a large hysteresis in the capacitance change, and the temperature dependence of the capacitance was observed. Very large conductive current was observed at the voltage larger than 3V probably due to the residual monomers and the absorbed water molecules.