Non-linear transient current in thin polyimide films prepared by vapor deposition polymerization

Two kinds of thin polyimide films are prepared by vapor deposition polymerization. One is annealed in air, and the other is annealed in a vacuum during imidization procedure. We have investigated electrical conduction in the two kinds of samples with low frequency voltage, and the difference between them have been discussed from the view point of ionic conduction. The samples annealed in air shows lead of current phase that due to the accumulated ionic space charge in the vicinity of the Al oxide layer at the Al-polyimide boundary. The samples annealed in a vacuum show lower conductivity and an anomalous current peak. The mechanism responsible for the current peak has been discussed in terms of diffusion and drift of space charges accumulated near the electrodes.