Dielectric and conduction properties of pure polyimide films

Capacitors with an Al-polyimide-Al sandwich film structure have been fabricated: the top and the bottom aluminium electrodes were deposited by vacuum evaporation and the polyimide film was deposited by an isothermal immersion method. An X-ray diffractogram of the film indicates the amorphous nature of the polyimide film. Dielectric and ac conduction properties of polyimide capacitors in the frequency range 10kHz to 10MHz at various temperatures (303-423 K) are reported; the dc conduction at different voltages and at various temperatures (303-423 K) is given. The capacitance of the film decreases with increasing frequency but increases with increasing temperature. The ac conduction studies suggest that electron hopping is responsible for conduction while the dc conduction studies reveal that Poole-Frenkel conduction is predominant at high fields. The activation and zero field activation energies are also calculated. (C) 2001 Society of Chemical Industry.